Security Researcher Finds Critical Flaws in Sophos Anti-Virus Engine

Security vendor Sophos has plugged a series of security holes in its antivirus product that were uncovered by a security researcher. In some cases, these security holes could have been exploited to cause crashes or to remotely execute code, according to the researcher.

The bugs in Sophos Anti-Virus were uncovered by Tavis Ormandy, who posted a message about his findings on the Full Disclosure mailing list on Nov. 5 and detailed the vulnerabilities in a paper available here.

Sophos says it has already patched most of flaws discovered by Ormandy and will release patches for additional issues Nov. 28.

“Sophos claims that their products are deployed throughout health care, government, finance, and even the military,” wrote Ormandy, a security engineer at Google. “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, noncritical systems and never deployed on networks or environments where a complete compromise by adversaries would be inconvenient.”

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

“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,” he added.

Ormandy wrote that the report and his comments were his opinion and did not reflect the opinion of Google. So far, Sophos has not seen any of the vulnerabilities exploited in the wild.

The vulnerabilities include: a remote-code-execution vulnerability discovered in how the Sophos Anti-Virus engine scans malformed Visual Basic 6 compiled files; the Sophos Web protection and Web control Layered Service Provider (LSP) block page contained a cross-site scripting vulnerability; an issue with the buffer overflow protection system (BOPS) technology in Sophos Anti-Virus for Windows.

Ormandy also identified problems with how the Sophos engine interacted with address space layout randomization (ASLR) on Windows Vista and later OSes; an issue with how Sophos protection interacts with Internet Explorer’s Protected Mode; and vulnerabilities tied to how Sophos’ antivirus engine handles malformed Microsoft Windows CAB (Cabinet) files and Roshal ARchive (RAR) files.

Ormandy also uncovered a remote-code-execution vulnerability in the way Sophos’ antivirus engine scans malformed PDF files. He also provided examples of other malformed files that can cause the Sophos antivirus engine to halt that are being examined by Sophos experts.

On Nov. 28, Sophos is will roll out a fix for the files that are being examined.

Sophos on its Naked Security blog thanked Ormandy for his work and for disclosing the bugs to the company before releasing details publicly.

“As a security company, keeping customers safe is [Sophos’] primary responsibility,” the company stated. “As a result, Sophos experts investigate all vulnerability reports and implement the best course of action in the tightest time period possible.”

“The work of Tavis Ormandy, and others like him in the research community, who choose to work alongside security companies, can significantly strengthen software products,” according to Sophos. “On behalf of its partners and customers, Sophos appreciates Tavis Ormandy’s efforts and responsible approach.”