Security Experts:

Chrome Flaw Allowed Hackers to Run Malicious Code via PDFs

A serious Chrome vulnerability patched recently by Google allowed hackers to execute arbitrary code on a system by using malicious PDF documents.

The vulnerability, discovered by Aleksandar Nikolic of Cisco Talos, is a heap buffer overflow (CVE-2016-1681) affecting PDFium, the default PDF reader in the Chrome web browser.

The problem exists in the jpeg2000 image parser library (OpenJPEG) used by PDFium. According to researchers, OpenJPEG prevents the heap overflow in standalone builds, but the bug affects Chrome due to a special build process.

Experts say an attacker could have exploited the vulnerability for arbitrary code execution by embedding a specially crafted jpeg2000 image in a PDF document.

“The most effective attack vector is for the threat actor to place a malicious PDF file on a website and and then redirect victims to the website using either phishing emails or even malvertising,” Cisco said in a blog post.

Cisco Talos reported the issue on May 19 and Google addressed it on May 25 with the release of Chrome 51.0.2704.63, which also patches 41 other security flaws. The search giant has classified the vulnerability as “high severity” and awarded Nikolic $3,000 for his findings.

Google normally discloses the details of Chrome vulnerabilities after 14 weeks to give users enough time to update. However, researchers can request the details to be made public after two weeks, which Cisco has done.

Chrome is automatically updated at regular intervals on Windows and Mac systems, which means most users should be protected against attacks leveraging this vulnerability as long as they have restarted their web browser. Some organizations may have chosen to disable auto-updates so that new versions of Chrome can be tested before being deployed on endpoints.

On June 1, Google released an update for Chrome 51 to address 15 security holes, including two high severity cross-origin bypass issues in the Blink web browser engine and extension bindings. An anonymous researcher and Mariusz Mlynski received $7,500 each for responsibly disclosing these vulnerabilities.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.