Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
===========================================================================
AUSCERT External Security Bulletin Redistribution
ESB-2007.0115 -- [Win][UNIX/Linux]
Multiple Vendor ClamAV CAB File Denial of Service Vulnerability
16 February 2007
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: ClamAV prior to 0.90
Publisher: iDEFENSE
Operating System: UNIX variants (UNIX, Linux, OSX)
Windows
Impact: Overwrite Arbitrary Files
Denial of Service
Access: Remote/Unauthenticated
CVE Names: CVE-2007-0897 CVE-2007-0898
Original Bulletin:
http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=475
http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=476
Comment: This bulletin contains details of two ClamAV vulnerabilities. An
updated version of ClamAV is available from the ClamAV website:
http://www.clamav.net/download/
- --------------------------BEGIN INCLUDED TEXT--------------------
Multiple Vendor ClamAV CAB File Denial of Service Vulnerability
iDefense Security Advisory 02.15.07
http://labs.idefense.com/intelligence/vulnerabilities/
Feb 15, 2007
I. BACKGROUND
Clam AntiVirus is a multi-platform GPL anti-virus toolkit. The main purpose
of which is integration into electronic mail servers. More information
about ClamAV can be found at http://clamav.net/. Microsoft CAB files are
the native compressed file format for Windows.
II. DESCRIPTION
Remote exploitation of a resource consumption vulnerability in Clam
AntiVirus' ClamAV allows attackers to degrade the service of the clamd
scanner.
The vulnerability specifically exists due to a file descriptor leak. When
clam encounters a cabinet header with a record length of zero it will
return from a function without closing a local file descriptor. This can
be triggered multiple times, eventually using up all but three of its
available file descriptors. This prevents clam from scanning most
archives, including zip and tar files.
III. ANALYSIS
Exploitation allows attackers to degrade the functionality of the ClamAV
virus scanning service. Exploitation requires that attackers send a
specially constructed CAB file through an e-mail gateway or personal
anti-virus client using the ClamAV scanning engine.
When ClamAV is unable to scan an archive successfully because it has run
out of descriptors, it will return an error status. Several mail servers
that use clam were tested to see how they handled this status. Exim, as of
version 4.50, features an option to build clamd support into it. It will
reject a mail if clamd fails to scan it properly. Amavisd will also deny a
mail that clamd cannot properly scan. This vulnerability can be used to
deny service to users trying to send legitimate archives through the mail
gateway.
IV. DETECTION
iDefense has confirmed this vulnerability affects Clam AntiVirus ClamAV
v0.90RC1.1. All versions prior to the 0.90 stable release are suspected
to be
vulnerable.
V. WORKAROUND
iDefense is unaware of any effective workarounds for this issue.
VI. VENDOR RESPONSE
Clam AntiVirus has addressed this vulnerability in the version 0.90 stable
release.
VII. CVE INFORMATION
The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-0897 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org/), which standardizes names for
security problems.
VIII. DISCLOSURE TIMELINE
02/07/2007 Initial vendor notification
02/13/2007 Initial vendor response
02/15/2007 Coordinated public disclosure
IX. CREDIT
The discoverer of this vulnerability wishes to remain anonymous.
Get paid for vulnerability research
http://labs.idefense.com/methodology/vulnerability/vcp.php
Free tools, research and upcoming events
http://labs.idefense.com/
X. LEGAL NOTICES
Copyright © 2006 iDefense, Inc.
Permission is granted for the redistribution of this alert electronically.
It may not be edited in any way without the express written consent of
iDefense. If you wish to reprint the whole or any part of this alert in
any other medium other than electronically, please e-mail
customerservice@idefense.com for permission.
Disclaimer: The information in the advisory is believed to be accurate at
the time of publishing based on currently available information. Use of
the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on, this
information.
Multiple Vendor ClamAV MIME Parsing Directory Traversal Vulnerability
iDefense Security Advisory 02.15.07
http://labs.idefense.com/intelligence/vulnerabilities/
Feb 15, 2007
I. BACKGROUND
Clam AntiVirus is a multi-platform GPL anti-virus toolkit. ClamAV is often
integrated into mail gateways, and used to scan mail traffic for viruses.
More information about ClamAV is available from http://clamav.net/.
Multipurpose Internet Mail Extensions (MIME), is an internet standard for
sending email with non-text attachments, multi-part message bodies, and
non-ASCII character sets.
II. DESCRIPTION
Remote exploitation of a directory traversal vulnerability in Clam
AntiVirus' ClamAV allows attackers to overwrite files owned by the clamd
scanner.
The vulnerability specifically exists due to the lack of validation of the
id parameter string taken from a MIME header. When parsing a multi-part
message clam takes this string from the header and uses it to create a
local file. By sending a string such as "../../../../some/file" an
attacker can create or overwrite an arbitrary file owned by the clamd
process. Data from the message body is later written to this file.
III. ANALYSIS
Exploitation allows attackers to degrade the service of the ClamAV virus
scanning service. The most important mitigating factor is that the clam
process runs with the privileges of the clamav user and group. This group
has access to a limited subset of files on the host. A possible target for
overwriting is the virus database file. By overwriting this file an
attacker could then send a virus through the gateway without clam
recognizing it; this effectively denies service. Arbitrary viruses will be
allowed to pass through, creating a false sense of security.
IV. DETECTION
iDefense has confirmed this vulnerability affects Clam AntiVirus ClamAV
v0.88.6. All versions prior to the 0.90 stable release are suspected to be
vulnerable.
V. WORKAROUND
iDefense is unaware of any effective workarounds for this issue.
VI. VENDOR RESPONSE
Clam AntiVirus has addressed this vulnerability in the version 0.90 stable
release.
VII. CVE INFORMATION
The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-0898 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org/), which standardizes names for
security problems.
VIII. DISCLOSURE TIMELINE
02/07/2007 Initial vendor notification
02/13/2007 Initial vendor response
02/15/2007 Coordinated public disclosure
IX. CREDIT
The discoverer of this vulnerability wishes to remain anonymous.
Get paid for vulnerability research
http://labs.idefense.com/methodology/vulnerability/vcp.php
Free tools, research and upcoming events
http://labs.idefense.com/
X. LEGAL NOTICES
Copyright © 2006 iDefense, Inc.
Permission is granted for the redistribution of this alert electronically.
It may not be edited in any way without the express written consent of
iDefense. If you wish to reprint the whole or any part of this alert in
any other medium other than electronically, please e-mail
customerservice@idefense.com for permission.
Disclaimer: The information in the advisory is believed to be accurate at
the time of publishing based on currently available information. Use of
the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on, this
information.
- --------------------------END INCLUDED TEXT--------------------
You have received this e-mail bulletin as a result of your organisation's
registration with AusCERT. The mailing list you are subscribed to is
maintained within your organisation, so if you do not wish to continue
receiving these bulletins you should contact your local IT manager. If
you do not know who that is, please send an email to auscert@auscert.org.au
and we will forward your request to the appropriate person.
NOTE: Third Party Rights
This security bulletin is provided as a service to AusCERT's members. As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content. The decision to follow or act on information or advice
contained in this security bulletin is the responsibility of each user or
organisation, and should be considered in accordance with your organisation's
site policies and procedures. AusCERT takes no responsibility for consequences
which may arise from following or acting on information or advice contained in
this security bulletin.
NOTE: This is only the original release of the security bulletin. It may
not be updated when updates to the original are made. If downloading at
a later date, it is recommended that the bulletin is retrieved directly
from the author's website to ensure that the information is still current.
Contact information for the authors of the original document is included
in the Security Bulletin above. If you have any questions or need further
information, please contact them directly.
Previous advisories and external security bulletins can be retrieved from:
http://www.auscert.org.au/render.html?cid=1980
If you believe that your computer system has been compromised or attacked in
any way, we encourage you to let us know by completing the secure National IT
Incident Reporting Form at:
http://www.auscert.org.au/render.html?it=3192
===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072
Internet Email: auscert@auscert.org.au
Facsimile: (07) 3365 7031
Telephone: (07) 3365 4417 (International: +61 7 3365 4417)
AusCERT personnel answer during Queensland business hours
which are GMT+10:00 (AEST).
On call after hours for member emergencies only.
===========================================================================
-----BEGIN PGP SIGNATURE-----
Comment: http://www.auscert.org.au/render.html?it=1967
iQCVAwUBRdUr/ih9+71yA2DNAQKR8wP/Tn3/MmI7kRudm36nddB3+I+4571HCo72
TgjsmOXxwz4gOFtiZiOeG8Fxzc1wGrIvK0rjoZ5pC8asKB5CGg3B6HValeLptdSD
iU7XdzNXzh5HKnJwcDk1SiOwkLaley8GLwookkmOWNKipf9UPP13biVywUG6AzO7
GolwFi0Qc6M=
=pH2T
-----END PGP SIGNATURE-----