Adobe Ships Silent Fix for Critical PDF Reader Flaw

Adobe has released a software fix for what's described simply as "security vulnerabilities" in its ubiquitous Adobe Reader program, but has not issued public documentation on the risk severity.

The absence of a bulletin with details and severity ratings has raised eyebrows in the security research community.

The patch, included in Adobe Reader 8.1.2, plugs at least one known critical issue that allows rigged PDF files to be used in code execution attacks, says Kostya Kortchinsky, a vulnerability researcher at Immunity.

Kortchinsky, a penetration-testing specialist who writes exploits for Immunity's CANVAS attack tool, said he reverse-engineered Adobe's patch and found that it silently fixed a stack overflow that would normally carry a "highly critical" rating.

Immunity has already posted a proof-of-concept exploit to its CANVAS Early Updates subscribers.  eWEEK has tested the Immunity exploit and can confirm that it crashes an unpatched Adobe Reader when opened from Microsoft's Internet Explorer browser.

There are unconfirmed reports that this vulnerability is being exploited in the wild to launch drive-by malware downloads.

Inexplicably, Adobe has not yet released a public warning on its Security bulletins and advisories Web site. Adobe officials could not be reached to comment on the absence of an official advisory.

The only acknowledgment from Adobe that the update contains security fixes comes from this KB article that cites "a number of customer workflow issues and security vulnerabilities."

Adobe Reader 8.1.2 is available for Windows 2000 Service Pack 4, Windows XP Service Pack 2, Windows 2003 Server, Windows Vista and Macintosh 10.4.3.

According to statistics from Secunia's PSI (Personal Software Inspector), 61 percent of Windows users who use the scanning tool were running vulnerable versions of the Adobe Reader software.