Security Experts:

Mozilla Updates Firefox to Patch Critical Flaws

Mozilla released updates for the standard and ESR versions of Firefox last week to address vulnerabilities classified as having “critical” impact.

Earlier this month, researchers at Cisco’s Talos team reported finding several vulnerabilities in the Libgraphite library, used for font processing in Linux, OpenOffice, Firefox and other popular applications. Experts discovered a total of four vulnerabilities that can be exploited for arbitrary code execution and denial-of-service (DoS) attacks.

In the case of Firefox, the vulnerabilities affect Graphite 2 version 1.2.4, which is used in Firefox 42 and earlier, and Firefox Extended Support Release (ESR) 38.x prior to version 38.6.1.

“To exploit these vulnerabilities, an attacker simply needs the user to run a Graphite-enabled application that renders a page using a specially crafted font that triggers one of these vulnerabilities,” Cisco’s Yves Younan said in a blog post. “Since Mozilla Firefox versions 11-42 directly support Graphite, the attacker could easily compromise a server and then serve the specially crafted font when the user renders a page from the server (since Graphite supports both local and server-based fonts).”

Mozilla updated the Graphite 2 library to version 1.3.5 in Firefox 43, released in December, and in Firefox ESR 38.6.1, released last week.

Firefox ESR is a version of the Web browser intended for organizations that need extended support for mass deployments, such as businesses, schools and governments. This version is not recommended for regular users since new features and enhancements only became available several development cycles after the standard Firefox.

Mozilla’s advisory covering Graphite 2 vulnerabilities focuses on CVE-2016-1523, a heap-based buffer overflow that can be exploited via a malicious font. The company credited researcher Holger Fuhrmannek for reporting the flaw.

Mozilla has also updated the standard version of Firefox to 44.0.2 in order to address a critical same-origin policy violation (CVE-2016-1949) reported by Jason Pang of OneSignal.

“[Pang] reported that service workers intercept responses to plugin network requests made through the browser. Plugins which make security decisions based on the content of network requests can have these decisions subverted if a service worker forges responses to those requests,” Mozilla said in an advisory. “For example, a forged crossdomain.xml could allow a malicious site to violate the same-origin policy using the Flash plugin.”

Related: Mozilla Re-Enables Support for SHA-1 in Firefox

Related: Firefox Warns of Password Requests Over HTTP

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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.