Adobe Systems released new versions of Adobe Reader 10.x and 9.x on Tuesday, addressing four arbitrary code execution vulnerabilities and making several security-related changes to the product, including the removal of the bundled Flash Player component from the 9.x branch.
All of the vulnerabilities fixed in the newly released Adobe Reader 10.1.3 and Adobe Reader 9.5.1 versions could be exploited by an attacker to crash the application and potentially take control of the affected system, Adobe said in its APSB12-08 security bulletin. Users are advised to install these updates as soon as possible.
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The company also announced that Adobe Reader 9.5.1 no longer includes authplay.dll, a Flash Player library that was bundled with previous versions of the program to enable the rendering of Flash content embedded in PDF documents.
The presence of the authplay.dll component in Adobe Reader has caused some security issues in the past, primarily because of the inconsistent update schedules for Adobe Reader and Flash Player.
Authplay.dll contains much of the stand-alone Flash Player's code, which also means that it shares most of the latter's vulnerabilities. However, while Flash Player is patched by Adobe when needed, Adobe Reader used to follow a more strict quarterly update cycle.
This often resulted in situations where some known vulnerabilities got patched in Flash Player, but remained exploitable through authplay.dll for months, until the next scheduled update for Adobe Reader.
Such is the case with the new Adobe Reader 10.1.3 version, which incorporates three previous Flash Player security updates that were released separately during the last three months.
Starting with Adobe Reader 9.5.1, Adobe Reader 9.x will use the stand-alone Flash Player plug-in that's already installed on computers for browsers like Mozilla, Safari or Opera, in order to play Flash content in PDF files.
This functionality will not work with the ActiveX-based Flash Player plug-in for Internet Explorer or the special Flash Player plug-in version bundled with Google Chrome.
Adobe plans to remove authplay.dll from the 10.x branch of Adobe Reader in the future as well and is currently working on APIs (application programming interfaces) to make this possible, said David Lenoe, group manager for Adobe's Product Security Incident Response Team (PSIRT), in a blog post Tuesday.
Vulnerability management vendor Secunia welcomes Adobe's decision to remove authplay.dll from Adobe Reader, because it will make addressing Flash vulnerabilities easier for users, Secunia's chief security specialist, Carsten Eiram, said.
"However, the default option in Adobe Reader should be to not support Flash content in PDF files, requiring users to specifically enable this," Eiram said. "Most users do not need it and Flash content embedded in PDF files has historically been exploited as a vector to compromise Adobe Reader users' systems."
This is actually the approach Adobe has taken with the 3D content rendering feature. Starting with Adobe Reader 9.5.1, this feature has been disabled by default because it's not commonly used and can be exploited in certain circumstances, Lenoe said.
"We've seen 0-days targeting this part of the functionality and it seems to be one of the more flawed features," Eiram said. "We've for a long time been recommending users to disable the plugins used for 3D parsing."
In addition to making these security patches and changes, Adobe also decided to cancel its quarterly update cycle for Adobe Reader and Acrobat and return to its previous patch-as-needed policy. Future Adobe Reader updates will continued be released on the second Tuesday of the month, but it will no longer happen every four months.
"We will publish updates to Adobe Reader and Acrobat as needed throughout the year to best address customer requirements and keep all of our users safe," Lenoe said.
"The quarterly update cycle never worked for Adobe," Eiram said. "Vulnerability fixes should always be provided as quickly as possible; it's not justifiable to unnecessarily postpone a vulnerability fix for up to three months simply due to policy reasons."