Quick response to security incidents is considered one of the strong points
of the free software community. It is also seen as a vital component of a
site's defenses against attacks. With that in mind, it is worth taking a
look at how the recent CVS
vulnerability played out:
May 2
Stefan Esser discovers a vulnerability in CVS, up to versions
1.11.15 and 1.12.7. A buffer overflow in the "entry" line parsing code
would allow an attacker to execute arbitrary code on the system when
the "pserver" access technique is being used. Mr. Esser informs the
CVS developers, and is told almost immediately that a fix has been
prepared.
May 3
Various high-profile CVS sites are informed of the
problem and its fix.
May 12
A new patch is prepared after SourceForge discovers a problem with
the previous versions.
May 19
The "coordinated public disclosure" happens, just in time to screw
up the LWN publication deadline. Updates are released by Debian,
Fedora, Mandrake, Red Hat, Slackware, and SUSE.
May 20
Gentoo releases its updated cvs package.
May 27
CERT gets around to sending out an
advisory on the vulnerability.
A few quick conclusions can be drawn from this sequence of events:
The coordinated disclosure mechanism had some glitches in its early
days, but it seems to be working well now. The problem was kept quiet
for a couple of weeks, after which most major distributors were able
to issue patches almost simultaneously.
One may well wonder, again, what the relevance of CERT is; it took
just over a week to get an advisory out after the public disclosure.
By then, anybody who was paying attention had already closed the
hole.
Some distributions do not yet have updates out. These include
Conectiva, Whitebox, and Trustix. (Update: Trustix lacks an update because it does not ship CVS, our mistake). Red Hat Linux users are also
exposed; the Fedora Legacy project has not yet issued a cvs update.
The last item is somewhat troubling. Given the nature of this
vulnerability and the availability of information, no serious distributor
should have failed to have an update ready on the disclosure day. One can
thus conclude that some distributors are more serious than others. In
particular, it is worth noting that the projects which rework Red Hat
distributions and updates (Whitebox, CentOS, Fedora Legacy) have failed to
react to this vulnerability in a timely way. It may well be that, if you
lack the structure necessary to create a distribution in the first place,
you will be hard pressed to keep that distribution secure.
A stack-based buffer overflow exists in the ssl_util_uuencode_binary
function in ssl_util.c in Apache. When mod_ssl is configured to trust the
issuing CA, a remote attacker may be able to execute arbitrary code via a
client certificate with a long subject DN.
The xatitv program, part of the gatos package, fails to drop root privileges after an initialization failure. For added fun, it then calls system() with unsanitized environment variables.
jftpgw (an FTP proxy) contains a format string vulnerability which could allow the execution of arbitrary commands with the privileges of the server process.
MIT Kerberos 5 suffers from multiple buffer overflows which could lead to a remote root exploit, though the exploit looks difficult. Versions through krb5-1.3.3 are affected; see this advisory for more information.
Versions of apache 1 through 1.3.30 include several minor vulnerabilities, including the writing of unescaped data to the error log file, a denial of service vulnerability, and a parsing failure in Allow/Deny rules on big-endian, 64-bit platforms. See the apache 1.3.31 announcement for details.
CVS (through version 1.11.15 or 1.12.7) contains a remotely exploitable heap overflow vulnerability; see this advisory from Stefan Esser for details. If you are running cvs with the "pserver" protocol, a quick upgrade is recommended (dropping pserver is also a very good idea for security-conscious sites).
"fam" (file alteration monitor) watches files and directories for changes and lets interested applications know when something happens. This package has a flaw in its group handling that blocks some legitimate operations while, at the same time, exposing the names of files that should otherwise be invisible.
A buffer overflow exists in three Firebird database binaries
(gds_inet_server, gds_lock_mgr, and gds_drop) that is exploitable by
setting a large value to the INTERBASE environment variable. An attacker
could control program execution, allowing privilege escalation to the UID
of Firebird, full access to Firebird databases, and trojaning the Firebird
binaries. An attacker could use this to compromise other user or root
accounts. See also this bug
report.
GtkHTML is the HTML rendering widget used by the Evolution mail reader.
GtkHTML supplied with versions of Evolution prior to 1.2.4 contain a bug
when handling HTML messages. Alan Cox discovered that certain malformed
messages could cause the Evolution mail component to crash.
Evgeny Demidov discovered a potential buffer overflow in a Kerberos 4
component of heimdal, a free implementation of Kerberos 5. The
problem is present in kadmind, a server for administrative access to
the Kerberos database. This problem could perhaps be exploited to
cause the daemon to read a negative amount of data which could lead to
unexpected behavior.
Versions of ipsec-tools prior to 0.2.5 contain a vulnerability wherein the racoon utility fails to verify digital signatures on some packets. This hole can lead to unauthorized connections or man-in-the-middle attacks. See this advisory for details.
racoon does not check the length of ISAKMP headers. Attackers may be able
to craft an ISAKMP header of sufficient length to consume all available
system resources, causing a Denial of Service. This advisory contains additional
details.
kdelibs (and, thus, Konqueror) has a vulnerability where a hostile server can force the disclosure of cookies that should not be presented to it. KDE versions 3.1.3 and later contain a fix.
iDEFENSE identified a vulnerability in the Opera Web Browser that could
allow remote attackers to create or truncate arbitrary files. The KDE team
has found that similar vulnerabilities exists in all version of KDE, up to
KDE 3.2.2 inclusive. See this advisory for
more information.
KDE has issued a security advisory for all
versions of kdepim as distributed with KDE versions 3.1.0 through 3.1.4
inclusive. A carefully crafted .VCF file potentially enables local
attackers to compromise the privacy of a victim's data or execute arbitrary
commands with the victim's privileges. The Common Vulnerabilities and
Exposures project (cve.mitre.org) has assigned the name CAN-2003-0988 to
this issue.
The 2.4 and 2.6 kernels contain a
vulnerability in the iso9660 (CDROM) filesystem which can be used by a
local attacker to obtain root privileges. The exploit requires creating a
specially-crafted filesystem and getting the kernel to mount it. Many
systems are configured to automatically mount CDs on insertion, however, so
the possibility of this vulnerability being exploited by users with
physical access to the system is real. The 2.4.26 kernel contains the fix,
which will also be merged into the upcoming 2.6.6 release.
A locally exploitable integer overflow has been found the multicast code
of the Linux kernel versions 2.4.22 to 2.4.25 and 2.6.1 - 2.6.3. A
successful exploit could lead to full superuser privileges.
The kernel-utils package contains several utilities that can be used to
control the kernel or machine hardware. In Red Hat Linux 8.0 this package
contains user mode linux (UML) utilities.
The uml_net utility in kernel-utils packages with Red Hat Linux 8.0 was
incorrectly shipped setuid root. This could allow local users to control
certain network interfaces, add and remove arp entries and routes, and put
interfaces in and out of promiscuous mode.
All users of the kernel-utils package should update to these packages that
contain a version of uml_net that is not setuid root.
Alternatively, as a work-around to this vulnerability issue the following
command as root:
LHA is an archiving and compression utility for LHarc format archives. Ulf
Harnhammar discovered two stack buffer overflows and two directory
traversal flaws in LHA. See this advisory+patch for more details.
CAN-2004-0234: An attacker could exploit the buffer overflows by creating a
carefully crafted LHA archive in such a way that arbitrary code would be
executed when the archive is tested or extracted by a victim.
CAN-2004-0235: An attacker could exploit the directory traversal issues to
create files as the victim outside of the expected directory.
Glenn Randers-Pehrson discovered a problem in connection with 16-bit
samples from libpng, an interface for reading and writing PNG
(Portable Network Graphics) format files. The starting offsets for
the loops are calculated incorrectly which causes a buffer overrun
beyond the beginning of the row buffer.
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.
Matthew Galgoci of Red Hat discovered a Denial of Service (DoS)
vulnerability in versions of Mailman prior to 2.1. An attacker could send
a carefully-crafted message causing mailman to crash. The Common
Vulnerabilities and Exposures project (cve.mitre.org) has assigned the name
CAN-2003-0991 to this issue.
Apache's mod_python module could crash the httpd process if a specific,
malformed query string was sent.
The Apache Foundation has reported that mod_python may be prone to
Denial of Service attacks when handling a malformed query. Mod_python
2.7.9 was released to fix the vulnerability, however, because the
vulnerability has not been fully fixed, version 2.7.10 has been released.
Users of mod_python 3.0.4 are not affected by this vulnerability.
Mozilla 1.4 contains a few vulnerabilities, including disclosure of cookies to the wrong server, a scripting vulnerability which can allow an attacker to run arbitrary code, and an S/MIME vulnerability which can lead to remote denial of service or code execution attacks.
A vulnerability was discovered in mpg321, a command-line mp3 player,
whereby user-supplied strings were passed to printf(3) unsafely. This
vulnerability could be exploited by a remote attacker to overwrite
memory, and possibly execute arbitrary code. In order for this
vulnerability to be exploited, mpg321 would need to play a malicious
mp3 file (including via HTTP streaming).
The neon library (through version 0.24.5) contains a buffer overflow in its date parsing code, allowing arbitrary code execution when connecting to a hostile server. See this advisory for details. This vulnerability also affects related applications (such as cadaver).
Some some vulnerabilities exsist in the Nessus NASL scripting engine. To
exploit these flaws, an attacker would need to have a valid Nessus account
as well as the ability to upload arbitrary Nessus plugins in the Nessus
server (this option is disabled by default) or he/she would need to trick a
user somehow into running a specially crafted nasl script. Read the full
advisory for additional information.
netpbm is graphics conversion toolkit made up of a large number of
single-purpose programs. Many of these programs were found to create
temporary files in an insecure manner, which could allow a local
attacker to overwrite files with the privileges of the user invoking a
vulnerable netpbm tool.
From the advisory:
"During a pen-test we stumbled across a nasty bug in OpenSSH-portable
with PAM support enabled (via the --with-pam configure script switch). This
bug allows a remote attacker to identify valid users on vulnerable systems,
through a simple timing attack. The vulnerability is easy to exploit and
may have high severity, if combined with poor password policies and other
security problems that allow local privilege escalation."
Steve Grubb found some problems in the passwd program. Passwords given to
passwd via stdin are one character shorter than they are supposed to be.
He also discovered that pam may not have been sufficiently initialized to
ensure safe and proper operation. A few small memory leaks have been fixed
as well.
The postfix MTA, versions through 1.1.12 (but not 2.0) is subject to two remotely exploitable denial of service vulnerabilities; see this advisory from Michal Zalewski for details.
See the rsync homepage for the
April 2004
advisory: "There is a security problem in all versions prior to
2.6.1 that affects only people running a read/write daemon WITHOUT using
chroot. If the user privs that such an rsync daemon is using is anything
above "nobody", you are at risk of someone crafting an attack that could
write a file outside of the module's "path" setting (where all its files
should be stored). Please either enable chroot or upgrade to 2.6.1. People
not running a daemon, running a read-only daemon, or running a chrooted
daemon are totally unaffected."
Several unspecified cross-site scripting (XSS) vulnerabilities and a well
hidden SQL injection vulnerability were found in SquirrelMail versions
1.4.2 and lower. An XSS attack allows an attacker to insert malicious code
into a web-based application. SquirrelMail does not check for code when
parsing variables received via the URL query string.
The tar utility does not properly filter file names containing
"../", meaning that a hostile archive can, if unpacked by an
unsuspecting user, overwrite any file that is writable by that user. GNU
tar versions 1.13.19 and earlier are vulnerable; unzip through version 5.42
has the same vulnerability.
TCPDUMP v3.8.1 and earlier versions contain multiple flaws in the packet
display functions for the ISAKMP protocol. Upon receiving specially
crafted ISAKMP packets, TCPDUMP will try to read beyond the end of the
packet capture buffer and crash. More information is available in this Rapid7 advisory.
This vulnerability,
originally thought to be confined to BSD-derived systems, was first covered
in the July 26th Security
Summary. It is now known that Linux telnet daemons are vulnerable as
well.
Steve Grubb discovered two potential issues in the utempter program:
If the path to the device contained /../ or /./ or //, the program
was not exiting as it should. It would be possible to use something like
/dev/../tmp/tty0, and then if /tmp/tty0 were deleted and symlinked to
another important file, programs that have root privileges that do no
further validation can then overwrite whatever the symlink pointed to.
Several calls to strncpy without a manual termination of the string.
This would most likely crash utempter.
XChat is vulnerable to a stack overflow that may allow a remote attacker to
run arbitrary code. The SOCKS 5 proxy code in XChat is vulnerable to a
remote exploit. Users would have to be using XChat through a SOCKS 5
server, enable SOCKS 5 traversal which is disabled by default and also
connect to an attacker's custom proxy server. This vulnerability may allow
an attacker to run arbitrary code within the context of the user ID of the
XChat client.
A vulnerability exists in xine-lib where playing a specially crafted Real
RTSP stream could run malicious code as the user playing the stream. More
details can be found in this
advisory. The problem has been fixed in xine-lib 1-rc4.
Shaun Colley discovered a problem in xine-ui, the xine video player
user interface. A script contained in the package to possibly remedy
a problem or report a bug does not create temporary files in a secure
fashion. This could allow a local attacker to overwrite files with
the privileges of the user invoking xine.
Jaguar discovered a vulnerability in one component of xpcd, a PhotoCD
viewer. xpcd-svga, part of xpcd which uses svgalib to display
graphics on the console, would copy user-supplied data of arbitrary
length into a fixed-size buffer in the pcd_open function.
