CVE-2012-4216 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the gfxFont::GetFontEntry function in Mozilla Firefox before 17.0, Firefox ESR 10.x before 10.0.11, Thunderbird before 17.0, Thunderbird ESR 10.x before 10.0.11, and SeaMonkey before 2.14 allows remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption) via unspecified vectors.
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Analysis
by VulDB Data Team • 04/19/2021
The CVE-2012-4216 vulnerability represents a critical use-after-free flaw within Mozilla Firefox's graphics font handling subsystem, specifically in the gfxFont::GetFontEntry function. This vulnerability affects multiple Mozilla products including Firefox, Thunderbird, and SeaMonkey across various versions, creating a widespread security risk that could be exploited by remote attackers. The flaw occurs when the application attempts to access memory that has already been freed, leading to unpredictable behavior that can be leveraged for code execution or system instability. The vulnerability's impact extends beyond simple memory corruption as it can be triggered through unspecified vectors, making it particularly dangerous in web browsing environments where users may encounter malicious content without explicit knowledge.
The technical nature of this vulnerability stems from improper memory management within the font rendering engine, which is part of the broader category of memory safety issues classified under CWE-416. When the gfxFont::GetFontEntry function processes font entries, it fails to properly manage the lifecycle of allocated memory objects, creating a scenario where freed memory can be accessed again. This use-after-free condition typically occurs during font substitution or fallback mechanisms when the application attempts to retrieve font entries that have already been deallocated from memory. The heap memory corruption that results from this flaw can manifest in various ways including application crashes, memory corruption that affects program execution flow, or more critically, the possibility of arbitrary code execution through carefully crafted malicious content that exploits the memory corruption to inject and execute attacker-controlled code.
From an operational perspective, this vulnerability poses significant risks to organizations and individual users who rely on Mozilla-based applications for their daily computing activities. The remote exploitability of this flaw means that attackers can leverage it through web pages, email attachments, or other network-delivered content without requiring any special privileges or user interaction beyond visiting a malicious website. The vulnerability's presence in Firefox ESR (Extended Support Release) versions indicates that even long-term supported versions were not immune to this memory safety issue, potentially affecting enterprise environments where stability and support longevity are critical factors. Security professionals must consider this vulnerability as part of their threat modeling exercises, particularly when evaluating the risk of remote code execution in browser environments where users frequently access untrusted content.
The exploitation of this vulnerability aligns with several tactics described in the MITRE ATT&CK framework, particularly those related to privilege escalation and code execution through memory corruption attacks. Attackers can leverage the heap corruption to perform return-oriented programming or other advanced exploitation techniques, making this vulnerability particularly dangerous in targeted attack scenarios. Organizations should prioritize patch management for this vulnerability, as the affected versions include both standard releases and extended support releases that may remain in use for extended periods. The remediation approach requires immediate deployment of patched versions of Firefox, Thunderbird, and SeaMonkey, with careful consideration given to the potential for exploitation during the patching window. Security teams should also implement network monitoring and intrusion detection measures to identify potential exploitation attempts, as the vulnerability's remote nature makes it particularly suitable for automated attack campaigns that could affect large user bases simultaneously.