Adobe Issues Emergency Patch Following December Miss

Adobe today issued an emergency security update, kicking off the new year with an out-of-band software fix to button up two critical flaws in Adobe Acrobat and Reader.

The advisory—Security Bulletin for Adobe Acrobat and Reader (APSB19-02)—outlines two vulnerabilities, but gives very little detail on the issues. In a more detailed advisory sent out to media, the company acknowledged two researchers, Abdul-Aziz Hariri and Sebastian Apelt, who regularly submit vulnerability research to Trend Micro's Zero Day Initiative, thanking Hariri for "his defense-in-depth contribution to hardening JavaScript API restriction bypasses."

While Adobe typically releases updates for its software on a schedule mimicking Microsoft's regular cadence of the second Tuesday of the month, the latest patch appears to be an emergency release. The company stated that its analysts are unaware of any exploitation of the vulnerabilities in the wild.

"These updates address critical vulnerabilities," the company wrote in the advisory. "Successful exploitation could lead to arbitrary code execution in the context of the current user."

The vulnerability (CVE-2018-19725) discovered by Hariri, an internal ZDI researcher, "addresses an incomplete fix from a previous security patch," Brian Gorenc, director of Trend Micro's Zero Day Initiative, told Dark Reading via an e-mail interview. "It allows overwriting JavaScript Read-Only variables, which is somewhat rare."

The second vulnerability (CVE-2018-16011) had apparently reached the 120-day disclosure deadline, after which ZDI would have released details of the issue. "By releasing a patch today, Adobe avoided the 0day disclosure and corrected the incomplete December patch," Gorenc said. Adobe had included the vulnerability as one of the issues fixed by its Dec. 11 patch, according to a previous Adobe advisory.

Adobe did not release details of the software components fixed by the update. The vulnerabilities, however, sound similar to previous vulnerabilities investigated by the two researchers into a dynamically linked library (DLL) that allows indexing of content in PDF documents. The 2014-era library, Onix.dll, creates indexes for searching, according to one 2018 blog post by Hariri. The two researchers credited with finding the vulnerabilities had both been working on auditing the library, according to a later blog post written by Hariri in December.

"[W]hen the Catalog bugs went public, Sebastian Apelt reached out and mentioned that he was also researching the indexing attack surface," Hariri wrote. "What was fascinating about Sebastian's research is figuring out a way to bypass the restrictions Adobe thought they had in place to prevent parsing the Indexing files from JavaScript."

The language almost exactly matches Adobe’s acknowledgement of Hariri's work. 

ZDI, however, denied that the current vulnerabilities are connected to that previous research. "These bugs are unrelated to the bugs discussed in that blog," Gorenc said.

Vulns on the Rise

In 2018, the number of overall vulnerabilities reported publicly increased by more than 13% to 16,518, according to the latest data from the National Vulnerability Database. The vulnerability count will continue to increase throughout 2019 as more issues are retroactively reported.

While software vendors usually find the best way to patch a vulnerability, failing to close off all avenues of exploitation is not an uncommon occurrence. Researchers often find ways to work around the fixes created by software firms. And, sometimes, the only way to fix the issues is to remove a feature, Hariri wrote in his December post.

"It's amazing how much individual research can expose. Even the vendor thought that the attack surface was mitigated," he said. "Anyway, Adobe finally figured out a scientific way to fix the bugs in this attack surface—killing the whole parsing code."

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