CVE-2016-9079 in Firefox
Summary
by MITRE
A use-after-free vulnerability in SVG Animation has been discovered. An exploit built on this vulnerability has been discovered in the wild targeting Firefox and Tor Browser users on Windows. This vulnerability affects Firefox < 50.0.2, Firefox ESR < 45.5.1, and Thunderbird < 45.5.1.
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Analysis
by VulDB Data Team • 01/27/2025
The CVE-2016-9079 vulnerability represents a critical use-after-free flaw within the SVG animation processing component of Mozilla Firefox and related applications. This vulnerability specifically targets the handling of Scalable Vector Graphics elements during animation sequences, creating a scenario where freed memory locations can be accessed and potentially manipulated by malicious actors. The flaw manifests when the browser processes certain SVG animation attributes that trigger memory deallocation followed by subsequent access to the same memory regions, creating exploitable conditions for remote code execution. The vulnerability was particularly concerning due to its exploitation in the wild, targeting users of Firefox and Tor Browser on Windows operating systems, demonstrating that attackers had developed working exploit code for this specific flaw.
The technical implementation of this vulnerability stems from improper memory management within the SVG animation engine, where objects allocated in memory are freed before all references to them are properly invalidated. This creates a window of opportunity where malicious SVG content can trigger the freeing of memory structures while simultaneously attempting to access those same structures through animation handlers. The flaw exists in the way Firefox processes certain animation attributes that cause the browser to free memory associated with SVG elements while animation sequences are still active, leading to a state where freed memory can be reused or accessed by crafted malicious content. This type of vulnerability is classified under CWE-416 as use-after-free, which is a well-known class of memory safety issues that frequently leads to arbitrary code execution exploits.
The operational impact of this vulnerability extends beyond simple browser compromise, as it specifically targeted users of privacy-focused browsers like Tor Browser, which are often used by individuals who require enhanced security protections. Attackers could craft malicious websites or email attachments containing specially designed SVG content that would trigger the vulnerability when opened in affected browsers, potentially leading to complete system compromise. The exploitation was particularly effective against Windows users due to the specific memory layout and heap management characteristics of the Windows operating system, which made the use-after-free condition more predictable and exploitable. This vulnerability demonstrated the critical importance of keeping browser software updated, as the affected versions included Firefox 49.0.2 and earlier, Firefox ESR 45.4.1 and earlier, and Thunderbird 45.4.1 and earlier, all of which were widely deployed in enterprise and personal environments.
Mitigation strategies for CVE-2016-9079 required immediate patching of affected browser versions, with Mozilla releasing updates to Firefox 50.0.2, Firefox ESR 45.5.1, and Thunderbird 45.5.1 to address the memory management issues in SVG animation processing. Organizations should have implemented immediate security updates and ensured that all users of affected browsers were upgraded to patched versions. Additional protective measures included disabling SVG animations in browser settings, implementing content filtering systems to block suspicious SVG content, and monitoring for exploitation attempts in network traffic. The vulnerability highlighted the importance of maintaining updated browser security patches, as well as the need for robust input validation and memory management practices in web browser implementations. From an ATT&CK framework perspective, this vulnerability would map to techniques involving exploit development and privilege escalation, as successful exploitation could lead to full system compromise and persistence mechanisms. The widespread exploitation of this vulnerability also demonstrated the critical need for continuous security monitoring and rapid response protocols to address newly discovered browser vulnerabilities that could be leveraged for advanced persistent threats.