Adobe has issued an emergency update for its popular Reader PDF software that patched two critical vulnerabilities, including one attackers have exploited for weeks.
The more notable flaw fixed in Reader 9.4.1 for Windows and Mac OS X was a bug that hackers have been leveraging since late October using malicious PDF documents. Those attacks have taken advantage of a flaw in Reader's "authplay" component. Authplay is the interpreter that renders Flash content embedded within PDF files.
Successful attacks have dropped a Trojan horse and other malware on victimised Windows PCs.
Authplay has been targeted by malware makers several times this year, most recently in June. Then, Adobe shipped an emergency patch for Flash Player within a week, and followed with a fix for Reader and Acrobat two weeks later.
Adobe followed the same general timeline this time, patching Flash Player first on November 4, then Reader and Acrobat today.
Adobe has defended its two-stage patching -- which some have questioned because active authplay exploits are typically aimed at Reader, not Flash -- by explaining that the fix was first crafted by its Flash development team. The patched "authoplay.dll" file was then handed off to the Reader group to integrate and test with their product.
The second vulnerability addressed Tuesday had been disclosed on the Full Disclosure security mailing list earlier this month. At the time, Adobe said that the flaw could be used to crash Reader, but not Acrobat, and said it was unsure whether an exploit could compromise a computer running the PDF program.
Adobe repeated that analysis today. "These updates resolve a memory corruption vulnerability that could potentially lead to code execution," the company said in an advisory accompanying the updates.
Although Adobe tries to hew to a quarterly patch schedule for Reader and Acrobat, at times it's scuttled those plans to issue rush fixes for critical bugs. That wasn't the case here: Adobe made it a point to remind users that it will still release its next regularly-scheduled Reader update on Feb. 8, 2011.
Only the Windows and Mac versions of Reader and Acrobat were patched today. An updated Reader for Linux/Unix won't ship until Nov. 30. Adobe also postponed a patch for the older Adobe 8.x, which is vulnerable to the second bug.
"Adobe plans to address Adobe Reader version 8.x in the next release," the advisory read.
Neither bug affected the Android version of Reader that Adobe launched in August.
Reader was last patched Oct. 5 in a 23-fix update one security expert called a "double-whammy."
Adobe Reader and Acrobat for Windows and Mac OS X can be downloaded using the links included in Tuesday's advisory. Alternately, users can call up the programs' built-in update mechanisms to grab the new versions.