People who deal with systems security spend a lot of time worrying about
buffer overflows, format string vulnerabilities, file creation races, and
so on. These problems can all lead to the compromise of an important
system, with the usual array of unpleasant consequences. So conscientious
administrators pay attention to new vulnerabilities, apply their patches,
and so on.
This Register
article, however, serves as a good reminder that there are other
aspects to the security problem:
Nine in ten (90 per cent) of office workers at London's Waterloo
Station gave away their computer password for a cheap pen, compared
with 65 per cent last year.
What a pain; all that patching and careful administration, then the users
hand their passwords over to a stranger when asked. Unfortunately, patches
for loose-lipped users are hard to come by. The security advantages of
free software also fail to offer much help in the way of blabbermouth
mitigation.
Lack of security consciousness is a real problem. Careless users will not
increase your exposure to the next Internet worm. But an attacker who has
set his sites on a specific target may well want to have a little
discussion with your users. Pens are cheap, after all.
gkrellm-newsticker has two vulnerabilities: a denial of service problem and a failure to filter shell metacharacters which can allow an attacker to run arbitrary commands by way of a hostile (or compromised) news feed.
Colin Phipps discovered several problems in mime-support, that contains
support programs for the MIME control files 'mime.types' and 'mailcap'.
When a temporary file is to be used it is created insecurely, allowing
an attacker to overwrite arbitrary under the user id of the person
executing run-mailcap, most probably root. Additionally the program did
not properly escape shell escape characters when executing a command.
This is unlikely to be exploitable, though.
Sam Hocevar discovered a security problem in rinetd, an IP connection
redirection server. When the connection list is full, rinetd resizes the
list in order to store the new incoming connection. However, this is done
improperly, resulting in a denial of service and potentially execution of
arbitrary code.
Versions of the snort intrusion detection system through 2.0-rc1 contain buffer and heap overflow vulnerabilities which could lead to remote code execution. Sites running snort are advised to upgrade to 2.0.0 as soon as possible; see this CERT advisory for more information.
The BIND 4.9.8-OW2 patch and BIND 4.9.9 release (and thus 4.9.9-OW1)
include fixes for a libc related vulnerability which does not
affect Linux. Updates from
the Internet Software Consortium (ISC)
are available from here.
No release or branch of Openwall GNU/*/Linux (Owl) is known to be
affected, due to Olaf Kirch's fixes for this problem getting into the
GNU C library more than two years ago.
Unfortunatly that does not mean that Linux systems are not vulnerable.
Similar code, without Olaf Firch's fixes,
is in the glibc getnetbyXXX functions.
These functions are described in the SuSE alert as
"
used by very few applications only, such as ifconfig and ifuser,
which makes exploits less likely."
CERT Advisory: CA-2002-19
Buffer Overflow in Multiple DNS Resolver Libraries
A denial of service vulnerability exists in BitchX. Sending a malformed
RPL_NAMREPLY numeric 353 causes BitchX to segfault. This problem was
reported to panasync@efnet#bitchx on Jan 30 2003, as of this writing we are
unaware of any patches or workarounds provided by panasync and or any
members of #bitchx
Canna is a kana-kanji conversion server which is necessary for Japanese
language character input.
A buffer overflow bug in the Canna server up to and including version 3.5b2
allows a local user to gain the privileges of the user 'bin' which could
lead to further exploits. The Common Vulnerabilities and Exposures project
(cve.mitre.org) has assigned the name CAN-2002-1158 to this issue.
A lack of validation of requests has been found that affects Canna version
3.6 and earlier. A malicious remote user could exploit this vulnerability
to leak information, or cause a denial of service attack. (CAN-2002-1159)
The dvips utility uses the system() function improperly when managing fonts. An attacker who can craft the right sort of print job can use this vulnerability to execute commands under the UID used by the print system.
A vulnerability was found in EOG version 2.2.0 and earlier. A carefully
crafted filename passed to the program could lead to the execution of
arbitrary code. An attacker could exploit this because various packages
(Mutt, for example) make use of EOG for image viewing.
Timo Sirainen discovered several problems in EPIC, a popular client for
Internet Relay Chat (IRC). A malicious server could craft special reply
strings, triggering the client to write beyond buffer boundaries. This
could lead to a denial of service if the client only crashes, but may also
lead to executing of arbitrary code under the user id of the chatting user.
The SOCKS dissector in Ethereal 0.9.9 is susceptible to a format string
overflow. This vulnerability has been present in Ethereal since the SOCKS
dissector was introduced in version 0.8.7. It was discovered by Georgi
Guninski. Additionally, the NTLMSSP code is susceptible to a heap
overflow. All users of Ethereal 0.9.9 and below are encouraged to upgrade.
See the full
advisory for additional information.
Multiple vulnerabilities have been found in Ximian's Evolution Mail User
Agent, according to this
CoreLabs advisory.
"Three vulnerabilities were found that could lead to various forms of
exploitation ranging from denying to users the ability to read email,
provoke system unstability, bypassing security context checks for email
content and possibly execution of arbitrary commands on vulnerable
systems."
Ximian Evolution is a personal and
workgroup information management solution for Linux and UNIX-based
systems. The software integrates email, calendaring, meeting scheduling,
contact management, and task lists, in one application.
"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.
Versions of fetchmail prior to 6.2.0 have (yet another) buffer overflow vulnerability which can be exploited remotely via a suitably crafted message. See this advisory for details.
Jeff Johnson found a memory allocation problem and David Endler found a
stack overflow corruption problem in the file "Automatic File Content
Type Recognition Tool" version 3.41. Nalin Dahyabhai improved ELF section
and program header handling in file version 3.40. The folks at OpenPKG
believe that file versions without those modifications are vulnerable to
memory allocation and stack overflow problems which put security at risk.
A race
condition in rm may cause the root user to delete the whole filesystem.
The problem exists in the version of rm in
fileutils
4.1 stable and 4.1.6 development version. A patch
is available.
(First LWN
report: May 2).
Felix von Leitner, discovered a
potential division by zero bug in
code derived from the SunRPC library which is used in glibc.This bug could be
exploited to gain unauthorized root access to software linking to glibc.
Updating as soon as practical is a good idea.
Because SunRPC-derived XDR libraries are used by a variety of vendors in a variety of applications, this defect may lead to a number of differing security problems. Exploiting this vulnerability will lead to denial of service, execution of arbitrary code, or the disclosure of sensitive information.
CERT/CC Vulnerability Note VU#192995 Integer
overflow in xdr_array() function when deserializing the XDR stream
DNS stub resolvers from multiple vendors contain a buffer overflow
vulnerability. The impact of this vulnerability appears to be limited to
denial of service. (See CERT Vulnerability Note
VU#738331)
The BIND 4 and BIND 8.2.x stub resolver libraries, and other libraries such
as glibc 2.2.5 and earlier, libc, and libresolv, uses the maximum buffer
size instead of the actual size when processing a DNS response, which
causes the stub resolvers to read past the actual boundary ("read buffer
overflow"), allowing remote attackers to cause a denial of service
(crash).
An integer overflow in the xdrmem_getbytes() function, and possibly other
functions, of XDR (external data representation) libraries derived from
SunRPC, including libnsl, libc, and glibc, allows remote attackers to
execute arbitrary code via certain integer values in length fields
See
CAN-2003-0028 and CERT advisory
CA-2003-10 for more information.
Paul Szabo discovered insecure creation of a temporary file in
ps2epsi, a script that is distributed as part of gs-common which
contains common files for different Ghostscript releases. ps2epsiuses
a temporary file in the process of invoking ghostscript. This file
was created in an insecure fashion, which could allow a local attacker
to overwrite files owned by a user who invokes ps2epsi.
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.
The IMP IMAP server, versions 2.2.8 and prior, is vulnerable to SQL
injection; see this advisory for details.
Version 3.x is not vulnerable to this problem.
The KDE Security team has issued an advisory
on a vulnerability present in all versions of KDE that allow a remote
attacker to execute arbitrary commands under your account. KDE 3.0.5b and
KDE 3.1.1a have been released to address this problem. For KDE 2.2.2
patches to the KDE 2.2.2 sources have been made available.
KDE uses Ghostscript software for processing of PostScript (PS) and PDF
files in a way that allows for the execution of arbitrary commands that can
be contained in such files.
An attacker can prepare a malicious PostScript or PDF file which will
provide the attacker with access to the victim's account and privileges
when the victim opens this malicious file for viewing or when the victim
browses a directory containing such malicious file and has file previews
enabled.
An attacker can provide malicious files remotely to a victim in an e-mail,
as part of a webpage, via an ftp server and possible other means.
Version 4 of the Kerberos protocol contains a cryptographic weakness which enables a chosen-plaintext attack. A suitably equipped attacker can impersonate any principal in the realm. Another weakness allows the creation of false Kerberos tickets. Given the weaknesses in the cryptography, cross-realm authentication cannot be performed in a secure way.
Versions 2.2.x and 2.4.x of the Linux kernel contain a vulnerability in
ptrace() which may be exploited by a local user to obtain root
access. This announcement contains the
details and a patch for 2.4.20. For 2.2 users, 2.2.25 has been released
which contains the fix.
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:
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.
Karol Lewandowski discovered that psbanner, a printer filter that
creates a PostScript format banner and is part of LPRng, insecurely
creates a temporary file for debugging purpose when it is configured
as filter. The program does not check whether this file already
exists or is linked to another place writes its current environment
and called arguments to the file unconditionally with the user id
daemon.
The lprm command of the printing package lprold contains a buffer
overflow. This buffer overflow can be exploited by a local user, if the
printer system is set up correctly, to gain root privileges.
If lynx is given a url with some special characters on the command line, it
will include faked headers in the HTTP query. This feature can be used to
force scripts (that use Lynx for downloading files) to access the wrong
site on a web server with multiple virtual hosts.
The SuSE Security Team reviewed critical Perl modules, including the
Mail::Mailer package. This package contains a security hole which allows
remote attackers to execute arbitrary commands in certain circumstances.
This is due to the usage of mailx as default mailer which allows commands
to be embedded in the mail body.
Note that mail processing programs which use this package can be affected by this vulnerability; in particular, SpamAssassin is vulnerable if you use the -r or -w flags.
Versions of man prior to 1.51 contain a code execution vulnerability which can be exploited by a carefully crafted man file. See this advisory for the details.
mgetty is a getty replacement for use with data and fax modems.
mgetty can be configured to run an external program to decide whether or
not to answer an incoming call based on Caller ID information. Unpatched
versions of mgetty prior to 1.1.29 would overflow an internal buffer if the
caller name reported by the modem was too long.
Additionally, the faxspool script supplied with versions of mgetty prior to
1.1.29 used a simple permissions scheme to allow or deny fax transmission
privileges. This scheme was easily circumvented because the spooling
directory used for outgoing faxes was world-writable.
Rüdiger Kuhlmann, upstream developer of mICQ, a text based ICQ client,
discovered a problem in mICQ. Receiving certain ICQ message types
that do not contain the required 0xFE seperator causes all versions to
crash.
Core
Security Technologies has found a remotely exploitable buffer overflow
in mutt's IMAP client code. This Bugtraq post
contains additional information.
The problem has been fixed in Mutt 1.4.1 (stable) and 1.5.4 (unstable).
According to a
report on BugTraq, a vulnerability exists in
version 3.23.55 and earlier versions of the MySQL server. If the MySQL server is
launched by root, as it is often done by system startup scripts, any
database users with the "FILE" privilege can write a configuration file
(usually my.cnf) that causes the MySQL server to run under an arbitrary
user id, including the user id of the super-user, on the next restart.
Al Viro and Alan Cox discovered several maths overflow errors in
NetPBM, a set of graphics conversion tools. These programs are not
installed setuid root but are often installed to prepare data for
processing. These vulnerabilities may allow remote attackers to cause
a denial of service or execute arbitrary code.
Potentially exploitable buffer overflows exist in the Macromedia Flash
Player. The full advisory is here.
"The cumulative security patch is available today and addresses the
potential for exploits surrounding buffer overflows (read/write) and
sandbox integrity within the player, which might allow malicious users to
gain access to a user's computer. The possibility of running native code on
a users machine is a theoretical exploit, and extremely difficult to
execute in practice. There are no known examples of running such native
code from Macromedia Flash movies; however, even though this issue is
difficult and theoretical in nature only, we are encouraging users to
upgrade."
David Brumley and Dan Boneh of Stanford University have researched and
documented a timing attack on OpenSSL which allows local and remote
attackers to extract the RSA private key of a server. The OpenSSL RSA
implementation is generally vulnerable to these type of attacks unless RSA
blinding has been turned on. See this
paper (pdf format) for additional details.
Typically, RSA blinding is not enabled by OpenSSL based applications,
mainly because it is not obvious how to do so when using OpenSSL to provide
SSL/TLS. This problem affects mostly all applications using OpenSSL and
have to be rebuilded against the fixed OpenSSL version (where RSA blinding
is now enabled by default) or have to enable RSA blinding explicitly their
own.
The performance impact of RSA blinding appears to be small (a few percent
only) and the RSA functionality is still fully compatible. The Common
Vulnerabilities and Exposures (CVE) project assigned the id
CAN-2003-0147 to the problem.
The pam_xauth module is used to forward xauth information from user to user
in applications such as 'su'.
Andreas Beck discovered that versions of pam_xauth supplied with Red Hat
Linux since version 7.1 would forward authorization information from the
root account to unprivileged users. This could be used by a local attacker
to gain access to an administrator's X session. In order to exploit this
vulnerability, the attacker would have to get the administrator, as root,
to use su to the account belonging to the attacker.
Two vulnerabilities exists in the mail() PHP function. The first one allows
the execution of any program/script bypassing safe_mode restriction, the
second one may give an open-relay script if the mail() function is not
carefully used in PHP scripts. See this Bugtraq
report for more details. Note that this is a different vulnerability than the previous PHP mail() problem, which affected versions through 4.1.0.
A new set of buffer overflows has been discovered in PostgreSQL 7.2.2; they affect the circle_poly(), path_encode(), and path_addr() functions. Exploiting these overflows requires that the attacker first obtain a connection to the PostgreSQL server.
Zack Weinberg discovered that
os._execvpe from os.py uses a predictable name which could lead
to execution of arbitrary code. According to the Debian
advisory, the problem
was present in Python versions 1.5, 2.1 and 2.2.
usePerl has a
description of a vulnerability in the Safe.pm Perl module. It seems
that if a Safe compartment is used more than once, it ceases to be safe.
The problem is fixed in Safe 2.08.
Digital Defense Inc. has sent out an
advisory describing another remotely-exploitable buffer overrun in the
Samba server; all versions through 2.2.8 or 2.0.10 (or Samba-TNG 0.3.2) are
vulnerable. The Samba team has released Samba
2.2.8a with a fix for the problem; there is also a patch available for
the 2.0 series. An exploit is said to be circulating already, so applying
patches quickly would be a good idea.
There is yet another buffer overrun in sendmail; this one was discovered by Michal Zalewski.
From the CERT Advisory:
"There is a vulnerability in sendmail that can be exploited to cause
a denial-of-service condition and could allow a remote attacker to
execute arbitrary code with the privileges of the sendmail daemon,
typically root." Sendmail 8.12.9 was released with a fix for the problem.
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.
Andrew Griffiths and iDEFENSE Labs discovered a problem in tcpdump, a
powerful tool for network monitoring and data acquisition. An
attacker is able to send a specially crafted network packet which
causes tcpdump to enter an infinite loop.
In addition to the above problem the tcpdump developers discovered a
potential infinite loop when parsing malformed BGP packets. They also
discovered a buffer overflow that can be exploited with certain
malformed NFS packets.
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.
A problem has been discovered in the typespeed, a game that lets you
measure your typematic speed. By overflowing a buffer a local
attacker could execute arbitrary commands under the group id games.
VIM allows a user to set the modeline differently for each edited text file
by placing special comments in the files. Georgi Guninski found that these
comments can be carefully crafted in order to call external programs. This
could allow an attacker to create a text file such that when it is opened
arbitrary commands are executed.
From the ISS
advisory:
"Vixie Cron is a scheduling daemon that ships with several Linux
distributions. Vixie Cron version 3.0pl1 could allow a local attacker to
gain root privileges. Crontab fails to properly drop privileges in certain
cases after a crontab modification operation. A local attacker could
exploit this vulnerability to gain root privileges on the system since
crontab is installed setuid root."
Note: this vulnerability is dated May 07 2001, and was first mentioned in
LWN on the May 10,
2001 security page.
VNC is a tool for providing a remote graphical user interface. Two
vulnerabilities have been found in versions of VNC shipped by Red Hat.
The VNC server acts as an X server, but the script for starting it
generates an MIT X cookie (which is used for X authentication) without
using a strong enough random number generator. This could allow an
attacker to be able to more easily guess the authentication cookie.
The VNC DES authentication scheme is implemented using a challenge-response
architecture, producing a random and different challenge for each
authentication attempt. A bug in the function for generating the random
challenge caused the random seed to get reset to the current time on every
authentication attempt. Therefore, two authentication attempts within the
same second could receive the same challenge. An eavesdropper could
exploit this vulnerability by replaying the response, thereby gaining
authentication.
All users of VNC are advised to upgrade to these erratum packages, which
contain patches to correct these issues.
Versions of wget prior to 1.8.2-4 contain a bug that permits a malicious
FTP server to create or overwrite files anywhere on the local file system.
FTP clients must check to see if an FTP server's response to the NLST
command includes any directory information along with the list of filenames
required by the FTP protocol (RFC 959, section 4.1.3).
If the FTP client fails to do so, a malicious FTP server can send filenames
beginning with '/' or containing '/../' which can be used to direct a
vulnerable FTP client to write files (such as .forward, .rhosts, .shosts,
etc.) that can then be used for later attacks against the client machine.
The libgtop_daemon package is a GNOME
program which makes system information available remotely.
LWN reported the remotely exploitable format
string and buffer overflow vulnerabilities in that package
on December 6th.
On November 28th
disabling the libgtop_daemon on systems where it is running until
an update is available.
Many Linux systems do not run
libgtop by default, but applying the update is a good idea anyway.
The wwwoffle web proxy incorrectly processes HTTP PUT and POST requests
with negative Content Length values.
"It is believed
that an attacker could exploit this bug to gain remote wwwrun access
to the system wwwoffled is running on."
Ethan Benson discovered a problem in xfsdump, that contains administrative
utilities for the XFS filesystem. When filesystem quotas are enabled
xfsdump runs xfsdq to save the quota information into a file at the root of
the filesystem being dumped. The manner in which this file is created is
unsafe.
While fixing this, a new option ``-f path'' has been added to xfsdq(8) to
specify an output file instead of using the standard output stream. This
file is created by xfsdq and xfsdq will fail to run if it exists already.
The file is also created with a more appropriate mode than whatever the
umask happened to be when xfsdump(8) was run.
From this Bugtraq
posting:
"zlib contains a function called gzprintf(). This is similar in
behaviour to fprintf() except that by default, this function will smash the
stack if called with arguments that expand to more than Z_PRINTF_BUFSIZE
(=4096 by default) bytes."
