When a security bug is found in the kernel, a patch is usually available
within hours; the kernel developers rightly take these things very seriously.
Once the patch is available, the stable team typically releases a new kernel
within a week or so and this is one of the big advantages of open source.
Once in a while, however, a bug that has been fixed previously can creep
back into the source, open or closed, and is known as a 'regression'.
This week's 2.6.19.1 kernel
release has a fix for something
that looks an awful lot like a regression, but technically is not.
Back in July, LWN described
a security problem in the then-current 2.6.17 kernel. The issue was that
local users could configure their processes to write core dump files in
directories that they did not have write permissions for. As the article
described, this could be trivially exploited for local privilege escalation;
in short, a local root hole.
This bug was fixed by the following patch:
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1983,7 +1983,7 @@ asmlinkage long sys_prctl(int option, un
error = current->mm->dumpable;
break;
case PR_SET_DUMPABLE:
- if (arg2 < 0 || arg2 > 2) {
+ if (arg2 < 0 || arg2 > 1) {
error = -EINVAL;
break;
}
which prevented processes from setting the dumpable flag to two. That flag
governs whether core dumps are produced by the process; the special
value of two reflects an ability to dump core with root privileges, quite
possibly to directories that the user cannot normally write to. The code
did guard against overwriting existing files, for security reasons, but
did not consider the implications of allowing user processes to effectively
write anywhere.
The code which handles the dumpable flag lives in fs/exec.c in the
aptly named do_coredump() function:
At the end of September, a
patch by Andi Kleen was
applied to allow core dumps to be piped to a userspace process. This
patch had been, according to Andi, "hanging around for a long time" and
lacked the flag
in the call to filp_open(). The patch made it into 2.6.19-rc1
kernel and from there into 2.6.19.
The impact of the bug is relatively low as a root user would have to set
the dumpable flag to two via
/proc/sys/fs/suid_dumpable. This would allow user processes to write
core dumps anywhere, which is as designed, but also would allow them to
overwrite existing files, which is not. It probably is not very common
that admins need to configure things that way, but it certainly is not
completely outside the realm of possibility either.
As described in the patch, Alexey Dobriyan
used a list of warnings
gathered from compiling the kernel. The warnings were grepped for
'was set but never used' and the first entry in the list pointed to this
problem. The kernel produces enough warnings that problems like this tend
to be obscured in a sea of bogus or overly picky warnings.
This particular bug is not technically a regression as there never was a bug
that allowed this behavior until it was introduced in the patch. It has been
assigned
CVE-2006-6304
(as of this writing, it is just a reserved CVE with no information).
It is great to see folks scrutinizing warnings and looking for bugs in the
kernel, this is just the kind of thing that the 'many eyes make all bugs
shallow' theory is referring to.
It would be nice to see a kernel regression test suite that contained
test cases for bugs that have previously been fixed as that kind of thing
might have caught this bug. It is a difficult problem, however, and keeping
up with the number of bug fix patches would be daunting. Perhaps a regression
suite that focused on security fixes would be a good place to start.
A "stack overwrite" vulnerability in GnuPG (gpg) allows attackers to
execute arbitrary code via crafted OpenPGP packets that cause GnuPG to
dereference a function pointer from deallocated stack memory.
A stack overflow in the KFILE JPEG (kfile_jpeg) plugin in kdegraphics3, as
used by konqueror, digikam, and other KDE image browsers, allows remote
attackers to cause a denial of service (stack consumption) via a crafted
EXIF section in a JPEG file, which results in an infinite recursion.
Rhys Kidd discovered a vulnerability in l2tpns, a layer 2 tunneling
protocol network server, which could be triggered by a remote user to
execute arbitrary code.
Luigi Auriemma has reported various boundary errors in load_it.cpp and
a boundary error in the "CSoundFile::ReadSample()" function in
sndfile.cpp. A remote attacker can entice a user to read crafted modules
or ITP files, which may trigger a buffer overflow resulting in the
execution of arbitrary code with the privileges of the user running the
application.
Laurent Butti, Jerome Raznieski and Julien Tinnes reported a buffer
overflow in the encode_ie() and the giwscan_cb() functions from
ieee80211_wireless.c. A remote attacker could send specially crafted
wireless WPA packets containing malicious RSN Information Headers (IE) that
could potentially lead to the remote execution of arbitrary code as the
root user.
The Ruby CGI library, cgi.rb, does not properly detect
boundaries in MIME multipart content. A remote attacker can
use this to cause a denial of service.
Multiple cross-site scripting (XSS) vulnerabilities in SquirrelMail 1.4.0
through 1.4.9 allow remote attackers to inject arbitrary web script or HTML
via the mailto parameter in webmail.php, the session and delete_draft
parameters in compose.php, and unspecified vectors involving "a shortcoming
in the magicHTML filter."
From the Red Hat advisory: "A bug was found in Apache where an invalid Expect header sent to the server
was returned to the user in an unescaped error message. This could
allow an attacker to perform a cross-site scripting attack if a victim was
tricked into connecting to a site and sending a carefully crafted Expect
header."
An off-by-one error in the der_get_oid function in mod_auth_kerb 5.0 allows
remote attackers to cause a denial of service (crash) via a crafted
Kerberos message that triggers a heap-based buffer overflow in the
component array.
The Asterisk telephony PBX application has a heap overflow vulnerability
in the skinny channel driver. A remote attacker can use this to
arbitrarily execute code with the privileges of the Asterisk user.
See this
vulnerability report
for more information.
Steve Grubb discovered that netlink messages were not being checked for
their sender identity. This could lead to local users manipulating the
Avahi service.
The BusyBox 1.1.1 passwd command does not use a proper salt when generating
passwords. This would create an instance where a brute force attack could
take very little time.
A race condition in bzip2 1.0.2 and earlier allows local users to modify
permissions of arbitrary files via a hard link attack on a file while it is
being decompressed, whose permissions are changed by bzip2 after the
decompression is complete. Also specially crafted bzip2 archives may cause
an infinite loop in the decompressor.
Richard Harms discovered that cpio did not sufficiently validate file
properties when creating archives. Files with e. g. a very large size
caused a buffer overflow. By tricking a user or an automatic backup
system into putting a specially crafted file into a cpio archive, a
local attacker could probably exploit this to execute arbitrary code
with the privileges of the target user (which is likely root in an
automatic backup system).
The Vixie cron daemon does not check the return code from setuid(); if that call can be made to fail, a local attacker may be able to execute commands as root.
Will Drewry of the Google Security Team discovered several buffer overflows
in cscope, a source browsing tool, which might lead to the execution of
arbitrary code.
A buffer overflow in Cscope 15.5, and possibly multiple overflows, allows
remote attackers to execute arbitrary code via a C file with a long
#include line that is later browsed by the target.
Cyrus-SASL contains an unspecified vulnerability in the DIGEST-MD5
process that could lead to a Denial of Service. An attacker could possibly
exploit this vulnerability by sending specially crafted data stream to the
Cyrus-SASL server, resulting in a Denial of Service even if the attacker is
not able to authenticate.
The dovecot IMAP server has an error in its index cache file handling code which could be exploited by an authenticated user to execute arbitrary code. Only servers with the (non-default) mmap_disable=yes option setting are vulnerable.
The elinks text-mode browser has an arbitrary file access vulnerability
in the Elinks SMB protocol handler. If a user can be tricked into
visiting a specially crafted web page, arbitrary files may be read or
written with the user's permissions.
the AVI processing code in FFmpeg has a number of buffer overflow
vulnerabilities.
If an attacker can trick a user into loading a specially crafted
crafted AVI, arbitrary code can be executed with the user's privileges.
Several remote vulnerabilities have been discovered in freeradius, a
high-performance RADIUS server, which may lead to SQL injection or denial
of service.
The FreeType library has several integer overflow vulnerabilities.
If a user can be tricked into installing a specially
crafted font file, arbitrary code can be executed with the privilege
of the user.
Ftpd is vulnerable to a privilege escalation attack,
an incorrect seteuid() call can be used by an FTP user to gain
unauthorized access to files or directories.
The fastjar utility found in the GNU compiler collection does not perform adequate file path checking, allowing the creation or overwriting of files outside of the current directory tree.
A buffer overflow in dwarfread.c and dwarf2read.c debugging code in GNU
Debugger (GDB) 6.5 allows user-assisted attackers, or restricted users, to
execute arbitrary code via a crafted file with a location block
(DW_FORM_block) that contains a large number of operations.
A format string vulnerability has been discovered in gedit. Calling
the program with specially crafted file names caused a buffer
overflow, which could be exploited to execute arbitrary code with the
privileges of the gedit user.
GnuPG has a buffer overflow vulnerability. If a user can be tricked
into running gpg interactively on a specially crafted message,
arbitrary code can be executed with the user's privileges.
Stack-based buffer overflow in the ps_gettext function in ps.c for GNU gv
3.6.2, and possibly earlier versions, allows user-assisted attackers to
execute arbitrary code via a PostScript (PS) file with certain headers that
contain long comments, as demonstrated using the DocumentMedia header.
Tavis Ormandy of the Google Security Team discovered two denial of service
flaws in the way gzip expanded archive files. If a victim expanded a
specially crafted archive, it could cause the gzip executable to hang or
crash.
Tavis Ormandy of the Google Security Team discovered several code execution
flaws in the way gzip expanded archive files. If a victim expanded a
specially crafted archive, it could cause the gzip executable to crash or
execute arbitrary code.
zgrep in gzip before 1.3.5 does not handle shell metacharacters like '|'
and '&' properly when they occurred in input file names. This could be
exploited to execute arbitrary commands with user privileges if zgrep is
run in an untrusted directory with specially crafted file names.
Daniel Kobras discovered multiple buffer overflows in ImageMagick's SGI
file format decoder. By tricking a user or an automated system into
processing a specially crafted SGI image, this could be exploited to
execute arbitrary code with the user's privileges.
Multiple buffer overflows in GraphicsMagick before 1.1.7 and ImageMagick
6.0.7 allow user-assisted attackers to cause a denial of service and
possibly execute execute arbitrary code via (1) a DCM image that is not
properly handled by the ReadDCMImage function in coders/dcm.c, or (2) a
PALM image that is not properly handled by the ReadPALMImage function in
coders/palm.c.
M. Joonas Pihlaja discovered that imlib2 did not sufficiently verify the
validity of ARGB, JPG, LBM, PNG, PNM, TGA, and TIFF images. If a user
were tricked into viewing or processing a specially crafted image with
an application that uses imlib2, the flaws could be exploited to execute
arbitrary code with the user's privileges.
Kate / Kwrite, as shipped with KDE 3.2.x up to including 3.4.0, creates a file backup before saving a modified file. These backup files are created with default permissions, even if the original file had more strict permissions set. See this advisory for more information.
A buffer overflow in the bridging code in kernels through 2.6.18.3 can lead to a denial of service or potential code execution. The 2.6.18.4 kernel contains the fix.
Sridhar Samudrala discovered a local denial of service vulnerability
in the handling of SCTP sockets. By opening such a socket with a
special SO_LINGER value, a local attacker could exploit this to crash
the kernel. (CVE-2006-4535)
Kirill Korotaev discovered that the ELF loader on the ia64 and sparc
platforms did not sufficiently verify the memory layout. By attempting
to execute a specially crafted executable, a local user could exploit
this to crash the kernel. (CVE-2006-4538)
Some vulnerabilities were discovered in the Linux 2.6 kernel:
There are possibly exploitable bugs in the netfilter for IPv6 code.
(CVE-2006-4572)
The ATM subsystem of the Linux kernel could allow a remote attacker to
cause a Denial of Service (panic) via unknown vectors that cause the ATM
subsystem to access the memory of socket buffers after they are freed.
(CVE-2006-4997)
The ftdi_sio driver (usb/serial/ftdi_sio.c) in Linux kernel 2.6.x up to
2.6.17, and possibly later versions, allows local users to cause a denial
of service (memory consumption) by writing more data to the serial port
than the driver can handle, which causes the data to be queued.
From the MOKB-05-11-2006
advisory: "The ISO9660 filesystem handling code of the Linux
2.6.x kernel fails to properly handle corrupted data structures, leading to
an exploitable denial of service condition. This particular vulnerability
seems to be caused by a race condition and a signedness issue. When
performing a read operation on a corrupted ISO9660 fs stream, the
isofs_get_blocks() function will enter an infinite loop when
__find_get_block_slow() callback from sb_getblk() fails ("due to various
races between file io on the block device and getblk")."
Previous versions of the kernel package are subject to several
vulnerabilities. Certain malformed UDF filesystems can cause the system to
crash (denial of service). Malformed CDROM firmware or USB storage devices
(such as USB keys) could cause system crash (denial of service), and if
they were intentionally malformed, can cause arbitrary code to run with
elevated privileges. In addition, the SCTP protocol is subject to a remote
system crash (denial of service) attack.
The KOffice office suite has an integer overflow
vulnerability. If an attacker can trick a user into opening a
specially crafted PowerPoint (PPT) file, KOffice can be caused to crash or
possibly execute arbitrary code with the user's privileges.
Some kerberos applications fail to check the results of setuid() calls, with the result that, if that call fails, they could continue to execute as root after thinking they had switched to a nonprivileged user. A local attacker who can cause these calls to fail (through resource exhaustion, presumably) could exploit this bug to gain root privileges.
Szymon Zygmunt and Michal Bartoszkiewicz discovered a memory alignment
error in libgadu (from ekg, console Gadu Gadu client, an instant
messaging program) which is included in gaim, a multi-protocol instant
messaging client, as well. This can not be exploited on the x86
architecture but on others, e.g. on Sparc and lead to a bus error,
in other words a denial of service.
The GNOME library libgsf, which is used for writing structured file
formats, has a heap buffer overflow that can be exploited for the
purpose of executing arbitrary code.
Several buffer overflows were found in libmms. By tricking a user into
opening a specially crafted remote multimedia stream with an application
using libmms, a remote attacker could overwrite an arbitrary memory portion
with zeros, thereby crashing the program.
Steve Rigler discovered that the PAM module for authentication against
LDAP servers processes PasswordPolicyReponse control messages incorrectly,
which might lead to an attacker being able to login into a suspended
system account.
In pngrutil.c, the function png_decompress_chunk() allocates
insufficient space for an error message, potentially overwriting stack
data, leading to a buffer overflow.
A heap based buffer overflow bug was found in the way libpng strips alpha
channels from a PNG image. An attacker could create a carefully crafted PNG
image file in such a way that it could cause an application linked with
libpng to crash or execute arbitrary code when the file is opened by a
victim.
The t2p_write_pdf_string function in libtiff 3.8.2 and earlier is vulnerable
to a buffer overflow. Attackers can use a TIFF file with UTF-8 characters
in the DocumentName tag to overflow a buffer, causing a denial of service,
and possibly the execution of arbitrary code.
LibVNCServer fails to properly validate protocol types effectively
letting users decide what protocol to use, such as "Type 1 - None".
LibVNCServer will accept this security type, even if it is not offered
by the server.
Yuuichi Teranishi discovered a flaw in libxml2 versions prior to 2.6.6.
When fetching a remote resource via FTP or HTTP, libxml2 uses special
parsing routines. These routines can overflow a buffer if passed a very
long URL. If an attacker is able to find an application using libxml2 that
parses remote resources and allows them to influence the URL, then this
flaw could be used to execute arbitrary code.
libxml2 prior to version 2.6.14 has multiple buffer overflow
vulnerabilities, if a local user passes a specially crafted
FTP URL, arbitrary code may be executed.
Derek Abdine discovered that the NVIDIA Xorg driver did not correctly
verify the size of buffers used to render text glyphs. When displaying
very long strings of text, the Xorg server would crash. If a user were
tricked into viewing a specially crafted series of glyphs, this flaw
could be exploited to run arbitrary code with root privileges.
An arbitrary command execute bug was found in the lynx "lynxcgi:" URI
handler. An attacker could create a web page redirecting to a malicious URL
which could execute arbitrary code as the user running lynx.
Jean-David Maillefer discovered a format string bug in the
date_format() function's error reporting. By calling the function with
invalid arguments, an authenticated user could exploit this to crash
the server.
MySQL 4.1 before 4.1.21 and 5.0 before 5.0.24 allows a local user to access
a table through a previously created MERGE table, even after the user's
privileges are revoked for the original table, which might violate intended
security policy (CVE-2006-4031).
MySQL 4.1 before 4.1.21, 5.0 before 5.0.25, and 5.1 before 5.1.12, when run
on case-sensitive filesystems, allows remote authenticated users to create
or access a database when the database name differs only in case from a
database for which they have permissions (CVE-2006-4226).
MySQL 5.0.18 and earlier allows local users to bypass logging mechanisms
via SQL queries that contain the NULL character, which are not properly
handled by the mysql_real_query function. NOTE: this issue was originally
reported for the mysql_query function, but the vendor states that since
mysql_query expects a null character, this is not an issue for mysql_query.
Kurt Fitzner discovered that the NBD (network block device) server did not
correctly verify the maximum size of request packets. By sending specially
crafted large request packets, a remote attacker who is allowed to access
the server could exploit this to execute arbitrary code with root
privileges.
slapd in OpenLDAP before 2.3.25 allows remote authenticated users with
selfwrite Access Control List (ACL) privileges to modify arbitrary
Distinguished Names (DN).
Several vulnerabilities have been discovered in OpenOffice.org, a free
office suite.
It turned out to be possible to embed arbitrary BASIC macros in
documents in a way that OpenOffice.org does not see them but executes them
anyway without any user interaction. (CVE-2006-2198)
It is possible to evade the Java sandbox with specially crafted Java
applets. (CVE-2006-2199)
Loading malformed XML documents can cause buffer overflows and cause a
denial of service or execute arbitrary code. (CVE-2006-3117)
packet.c in ssh in OpenSSH allows remote attackers to cause a denial of
service (crash) by sending an invalid protocol sequence with
USERAUTH_SUCCESS before NEWKEYS, which causes newkeys[mode] to be NULL.
An unspecified vulnerability in portable OpenSSH before 4.4, when running
on some platforms, allows remote attackers to determine the validity of
usernames via unknown vectors involving a GSSAPI "authentication abort."
From the OpenSSH 4.5 announcement: "Fix a bug in the sshd privilege separation monitor that weakened its
verification of successful authentication. This bug is not known to
be exploitable in the absence of additional vulnerabilities."
Openssh 4.4 fixes some
security issues, including a pre-authentication denial of service, an
unsafe signal hander and on portable OpenSSH a GSSAPI authentication abort
could be used to determine the validity of usernames on some platforms.
OpenSSL has a number of denial of service vulnerabilities including:
two vulnerabilities involving invalid ASN.1 structures, a buffer overflow
in the SSL_get_shared_ciphers() function and an SSLv2 client crash that
can be caused by a malicious server.
The file_exists and imap_reopen functions in PHP before 5.1.5 do not check
for the safe_mode and open_basedir settings, which allows local users to
bypass the settings (CVE-2006-4481).
A buffer overflow in the LWZReadByte function in ext/gd/libgd/gd_gif_in.c
in the GD extension in PHP before 5.1.5 allows remote attackers to have an
unknown impact via a GIF file with input_code_size greater than
MAX_LWZ_BITS, which triggers an overflow when initializing the table array
(CVE-2006-4484).
The stripos function in PHP before 5.1.5 has unknown impact and attack
vectors related to an out-of-bounds read (CVE-2006-4485).
The Hardened-PHP Project discovered buffer overflows in
htmlentities/htmlspecialchars internal routines to the PHP Project. Of
course the whole purpose of these functions is to be filled with user
input. (The overflow can only be when UTF-8 is used)
It was discovered that phpbb2, a web based bulletin board, insufficiently
sanitizes values passed to the "Font Color 3" setting, which might lead to
the execution of injected code by admin users.
The phpbb2 web forum has a number of vulnerabilities including:
a web script injection problem, a protection mechanism bypass, a
security check bypass, a remote global variable bypass, cross site
scripting vulnerabilities, an SQL injection vulnerability,
a remote regular expression modification problem, missing input
sanitizing, and a missing request validation problem.
The PostgreSQL team has put out a set of "urgent updates" (in the form of the 7.3.15, 7.4.13, 8.0.8, and 8.1.4 releases) closing a
newly-discovered set of SQL injection issues. Details about the problem
can be found on the
technical information page; in short: multi-byte encodings can be used
to defeat normal string sanitizing techniques. The update fixes one problem
related to invalid multi-byte characters, but punts on another by simply
disallowing the old, unsafe technique of escaping single quotes with a
backslash.
A denial of service (DoS) vulnerability exists in the FTP server ProFTPD, up
to and including version 1.3.0. The flaw is due to both a potential bus
error and a definitive buffer overflow in the code which determines the FTP
command buffer size limit. The vulnerability can be exploited only if the
"CommandBufferSize" directive is explicitly used in the server
configuration.
An error was found in the RPM library's handling of query reports. In
some locales, certain RPM packages would cause the library to crash. If
a user was tricked into querying a specially crafted RPM package, the
flaw could be exploited to execute arbitrary code with the user's
privileges.
The CGI library in Ruby 1.8 allowed a remote attacker to cause a denial of
service via an HTTP request with a multipart MIME body that contained an
invalid boundary specifier, which would result in an infinite loop and CPU
consumption.
The useradd tool from the shadow-utils package has a potential security
problem. When a new user's mailbox is created, the permissions are
set to random garbage from the stack, potentially allowing the
file to be read or written during the time before fchmod() is called.
Teemu Salmela discovered that tar still handles the deprecated
GNUTYPE_NAMES record type. This record type could be used to create
symlinks that would be followed while unpacking a tar archive. If a user
or an automated system were tricked into unpacking a specially crafted tar
file, arbitrary files could be overwritten with user privileges.
Numerous vulnerabilities have been found in the Mozilla JavaScript and HTML
rendering code, leading to possible remote code execution attacks. This CERT advisory contains details.
It was discovered that Trac, a wiki and issue tracking system for
software development projects, performs insufficient validation against
cross-site request forgery, which might lead to an attacker being able
to perform manipulation of a Trac site with the privileges of the
attacked Trac user.
A buffer overflow in UnZip 5.50 and earlier allows local users to execute
arbitrary code via a long filename command line argument. NOTE: since the
overflow occurs in a non-setuid program, there are not many scenarios under
which it poses a vulnerability, unless unzip is passed long arguments when
it is invoked from other programs.
xtensive testing of libwww's handling of multipart/byteranges content from
HTTP/1.1 servers revealed multiple logical flaws and bugs in
Library/src/HTBound.c
The wv library has an integer overflow vulnerability in the DOC
file parser. If a user can be tricked into opening a maliciously
crafted MSWord file, a remote attacker can execute arbitrary code
with the privileges of the user.
A buffer overflow was discovered in the Real Media input plugin in
xine-lib. If a user were tricked into loading a specially crafted stream
from a malicious server, the attacker could execute arbitrary code with the
user's privileges.
xine-lib does an improper input data boundary check on
MPEG streams. A specially crafted MPEG file can be
created that can cause arbitrary code execution when the
file is accessed.
Several format string vulnerabilities have been discovered in xine-ui,
the user interface of the xine video player, which may cause a denial
of service.
A race condition allows local users to see error messages generated during
another user's X session. This could allow potentially sensitive
information to be leaked.
Several X.org libraries and X.org itself contain system calls to
set*uid() functions, without checking their result. Local users could
deliberately exceed their assigned resource limits and elevate their
privileges after an unsuccessful set*uid() system call. This requires
resource limits to be enabled on the machine.
There is a buffer overflow in the Xrender extension of the X.Org server; any process which is able to connect to the server may be able to exploit this overflow to run arbitrary code. Since the X server runs as root on most systems, this vulnerability could be exploited to gain root access. See the X.Org advisory for more information.
iDefense reported two integer overflow
flaws in the way the X.org server processed CID font files. A malicious
authorized client could exploit this issue to cause a denial of service
(crash) or potentially execute arbitrary code with root privileges on the
X.org server.
