Foxit PDF viewer open to attack, say researchers

Computerworld - Security researchers today warned of several vulnerabilities in Foxit, a free PDF document viewer that has been recommended as an alternative to Adobe Reader, which currently contains an unpatched critical bug of its own.

Foxit Software Co. patched its namesake today to plug three holes.

One of the three vulnerabilities is in the same JBIG2 image compression format fingered by researchers last month as the root of the bug in Adobe System Inc.'s popular Reader and Acrobat applications. The flaw in Adobe's software, which has been exploited by hackers since at least early January, will not be patched until Wednesday, according to Adobe's schedule.

The Foxit and Adobe bugs are unrelated, however, except for the fact that they are both in the code that parses JBIG2 images, said Thomas Kristensen, chief technology officer at Secunia, the Danish company that reported the flaw to Foxit. "It is a completely different vulnerability related to JBIG2," Kristensen said in an e-mail today.

It was Adobe's confirmation of its bug that prompted Secunia researchers to dig into other PDF viewers. "We did, however, start the research in Foxit out of curiosity based on the Adobe vulnerability, and discovered this new vulnerability," Kristensen said. Secunia reported the bug to Foxit on Feb. 27.

Kristensen declined to offer more information on the Foxit flaw, or the path that Secunia researchers took in finding it.

The remaining two bugs in Foxit were reported Feb. 18 by Core Security Technologies, a developer of penetration testing software. One of the vulnerabilities can trigger a buffer overflow, while the other could be used by attackers to circumvent security warnings.

Foxit has posted patched versions of Foxit 3.0 and Foxit 2.3 on its Web site.

Ironically, some experts have urged users to discard Adobe Reader for Foxit or other free PDF-viewing applications. For its part, Adobe has recommended that users disable JavaScript capabilities in Reader and Acrobat until a patch is available. Even so, last week a Belgian researcher released proof-of-concept attack code that doesn't rely on JavaScript and can trigger the bug without requiring the user to actually open a malformed PDF.

Adobe plans to patch Version 9 of Reader and Acrobat March 11, and Versions 7 and 8 of the applications on March 18.

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