A Google security team is warning that Adobe has passed on fixing a number of vulnerabilities in its Reader software for viewing PDF documents.
Adobe released a new version of Reader on Tuesday that fixed about 20 vulnerabilities in the Mac and Windows versions of the product. Despite the large number of flaws addressed in the patches, a number of serious vulnerabilities remained untouched, according to an analysis released on Wednesday by Mateusz Jurczyk and Gynvael Coldwind of Google.
Google's interest in Reader is the result of having the PDF viewer embedded in the search engine's Chrome browser. Earlier this year, the Google team started testing the application for exploitable bugs exposed through crashes of the viewer.
While Adobe fixed vulnerabilities rated high and critical, lesser flaws were untouched. "Unfortunately, 16 more crashes affecting Windows, OS X, or both systems remain unpatched," the Google security team said.
Adobe acknowledged receiving a list of bugs from Google in late June and tackling "around 75 percent of the issues in the short time since the report came in."
"We plan to address the remaining issues in the next release of Adobe Reader and Acrobat," Adobe spokeswoman Wiebke Lips said. "Adobe is not aware of any exploits in the wild for any of the issues reported by Google," she said.
Google's policy is to give application developers 60 days to fix vulnerabilities before exposing the flaws. On June 21 and June 27, Google notified Adobe of a total of 60 reproducible crashes related to Reader bugs. Not all the flaws were serious security risks.
Being that Adobe does not plan to release any more patches before Aug. 27, Google decided it was in the best interest of Chrome users to release some details on the bugs and how to mitigate risks.
Besides skipping fixes on some of the flaws in Windows and OS X versions of Reader, on Tuesday Adobe did not patch any of the vulnerabilities reported by Google in the GNU Linux version of the product.
The Windows and OS X vulnerabilities are in older versions of Reader. Users of Adobe Reader X are less at risk. Nevertheless, Google felt that hackers specializing in bug hunting could find the vulnerabilities, adding urgency to the disclosure. "We have decided that it's in the best interest of users to be aware of these security issues without additional delay," the security team said.
Because there are no workarounds available for the unpatched vulnerabilities, Google recommended limiting use of Reader or at least not opening externally received PDF documents. In addition, the company recommended disabling the Reader browser extension for the time being.
"Users of Adobe Reader 9.x for Windows who are aware of the risk are advised to upgrade to Adobe Reader X, which provides a sandbox feature, making it more difficult - although not impossible -- to exploit these vulnerabilities," the security team said. "Unfortunately, the sandbox feature is not available for the newest versions of Adobe Reader for OS X or Linux."
Because none of the vulnerabilities reported by Google would let hackers bypass the Reader sandbox, Adobe believed it had time to release the additional patches. " We do not believe that the outstanding issues represent a serious risk to users," Lips said.
Reader users are notorious for using out-of-date and potentially insecure versions of the program. An analysis last year by antivirus company Avast Software found that only 40 percent of users had installed the patched Reader X, which was first released in 2010.
Adobe provides the option of automatic updates for the software.