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Category:   Application (Security)  >   Sophos Anti-Virus Vendors:   Sophos
Sophos Anti-Virus Bugs Let Remote Users Execute Arbitrary Code with Root Privileges and Conduct Cross-Site Scripting Attacks and Let Local Users Gain Elevated Privileges
SecurityTracker Alert ID:  1027725
SecurityTracker URL:  http://securitytracker.com/id/1027725
CVE Reference:   GENERIC-MAP-NOMATCH   (Links to External Site)
Date:  Nov 6 2012
Impact:   Disclosure of user information, Execution of arbitrary code via local system, Execution of arbitrary code via network, Modification of system information, Modification of user information, Root access via local system, Root access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  Exploit Included:  Yes  

Description:   Several vulnerabilities were reported in Sophos Anti-Virus. A remote user can execute arbitrary code on the target system. A local user can obtain elevated privileges on the target system. A remote user can conduct cross-site scripting attacks.

A remote user can create a specially crafted file that, when processed by the target anti-virus software, will trigger a buffer overflow or memory corruption error and execute arbitrary code on the target system. The code will run with root or System privileges.

Visual Basic executable, RAR, PDF, and Microsoft CAB file formats are affected.

On Windows-based systems, a local user can exploit a flaw in directory access permissions of the network update service to replace certain files and cause arbitrary code to be executed on the target system with System privileges.

The software does not properly filter HTML code from user-supplied input before displaying the input. A remote user can cause arbitrary scripting code to be executed by the target user's browser. The code will run in the security context of an arbitrary site. As a result, the code will be able to access the target user's cookies (including authentication cookies), if any, associated with the site, access data recently submitted by the target user via web form to the site, or take actions on the site acting as the target user.

On Windows-based systems, the Sophos Buffer Overflow Protection System (BOPS) effectively disables the operating system's Address Space Layout Randomization (ASLR) protections.

On Windows-based systems, the software installs a Layered Service Provider (LSP) that loads modules from a low-integrity writable directory, which effectively disables Internet Explorer's protected mode.

The original advisory is available at:

https://lock.cmpxchg8b.com/sophailv2.pdf

Tavis Ormandy reported these vulnerabilities.

Impact:   A remote user can execute arbitrary code on the target system with root or system privileges.

A local user can obtain System privileges on the target system.

A remote user can access the target user's cookies (including authentication cookies), if any, associated with an arbitrary site, access data recently submitted by the target user via web form to the site, or take actions on the site acting as the target user.

Solution:   The vendor has issued a fix, available via automatic update [roll out completed on October 26, 2012 for some vulnerabilities and roll out beginning on November 5, 2012 for other vulnerabilities].

No solution for the local privilege escalation vulnerability was available at the time of this entry.

[Editor's note: Some additional undisclosed file processing vulnerabilities are expected to be patched beginning November 28, 2012. No further details are available at the time of this entry.]

The vendor's advisory is available at:

http://nakedsecurity.sophos.com/2012/11/05/tavis-ormandy-sophos/

Vendor URL:  nakedsecurity.sophos.com/2012/11/05/tavis-ormandy-sophos/ (Links to External Site)
Cause:   Access control error, Boundary error, Input validation error, Randomization error
Underlying OS:   Linux (Any), UNIX (OS X), Windows (Any)

Message History:   This archive entry has one or more follow-up message(s) listed below.
Nov 9 2012 (Cisco Issues Advisory for Cisco IronPort) Sophos Anti-Virus Bugs Let Remote Users Execute Arbitrary Code with Root Privileges and Conduct Cross-Site Scripting Attacks and Let Local Users Gain Elevated Privileges   (Cisco Systems Product Security Incident Response Team <psirt@cisco.com>)
Cisco has described a configuration workaround for Cisco IronPort.



 Source Message Contents

Date:  Mon, 5 Nov 2012 16:14:17 +0100
Subject:  [Full-disclosure] multiple critical vulnerabilities in sophos products

List, I've completed the second paper in my series analyzing Sophos
Antivirus internals, titled "Practical Attacks against Sophos
Antivirus". As the name suggests, this paper describes realistic
attacks against networks using Sophos products.

The paper includes a working pre-authentication remote root exploit
that requires zero-interation, and could be wormed within the next few
days. I would suggest administrators deploying Sophos products study
my results urgently, and implement the recommendations.

I've also included a section on best practices for Sophos users,
intended to help administrators of high-value networks minimise the
potential damage to their assets caused by Sophos.

The paper is available to download at the link below.

https://lock.cmpxchg8b.com/sophailv2.pdf

A working exploit for Sophos 8.0.6 on Mac is available, however the
techniques used in the exploit easily transfer to Windows and Linux,
due to multiple critical implementation flaws described in the paper.
Testcases for the other flaws described in the paper are available on
request.

https://lock.cmpxchg8b.com/sophail-rev3-exploit.tar.gz

It is my understanding that Sophos plan to publish their own advice to
their customers today. I have not been given an opportunity to review
the advice in advance, so cannot comment on it's accuracy.

I have had a working exploit since September, but Sophos requested I
give them two months to prepare for this publication before discussing
it. A timeline of our interactions is included in the paper. I believe
CERT are also preparing an advisory. I'm currently working on the
third paper in the series, which I'll announce at a later date. Please
contact me if you would like to be a reviewer. I will add any last
minute updates to twitter, at http://twitter.com/taviso.

If you would like to learn more about Sophos internals, you can read
my previous paper in the series here
https://lock.cmpxchg8b.com/sophail.pdf

I've reproduced a section of the conclusion below.

Tavis.

Conclusion

As demonstrated in this paper, installing Sophos Antivirus exposes
machines to considerable risk. If Sophos do not urgently improve their
security posture, their continued deployment causes significant risk
to global networks and infrastructure.

In response to early access to this report, Sophos did allocate some
resources to resolve the issues discussed, however they were cearly
ill-equipped to handle the output of one co-operative, non-adversarial
security researcher. A sophisticated state-sponsored or highly
motivated attacker could devastate the entire Sophos user base with
ease.

Sophos claim their products are deployed throughout healthcare,
government, finance and even the military. The chaos a motivated
attacker could cause to these systems is a realistic global threat.
For this reason, Sophos products should only ever be considered for
low-value non-critical systems and never deployed on networks or
environments where a complete compromise by adversaries would be
inconvenient.

-- 
-------------------------------------
taviso@cmpxchg8b.com | pgp encrypted mail preferred
-------------------------------------------------------

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