CVE-2012-4218 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the BuildTextRunsScanner::BreakSink::SetBreaks function in Mozilla Firefox before 17.0, Thunderbird before 17.0, 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 vulnerability identified as CVE-2012-4218 represents a critical use-after-free condition within the Mozilla Firefox browser ecosystem, affecting versions prior to 17.0, as well as Thunderbird and SeaMonkey applications. This flaw resides in the BuildTextRunsScanner::BreakSink::SetBreaks function, which is responsible for handling text rendering operations in the browser's layout engine. The issue manifests when the application processes text content that triggers memory management operations in an improper sequence, creating opportunities for malicious exploitation through heap memory corruption.
The technical nature of this vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions where memory is accessed after it has been freed, and represents a classic heap corruption vulnerability. Attackers can leverage this flaw by crafting malicious web content that, when rendered by the affected browser versions, causes the application to free memory associated with text rendering structures and subsequently attempt to access that same memory location. This sequence creates a predictable pattern of memory corruption that can be exploited to execute arbitrary code with the privileges of the user running the vulnerable application.
From an operational perspective, the impact of this vulnerability extends beyond simple denial of service scenarios to enable remote code execution, making it particularly dangerous in web browsing contexts. The attack vector remains unspecified in the CVE description, suggesting that multiple methods could trigger the vulnerable code path, potentially including dynamically generated content, embedded media, or complex text formatting operations. The vulnerability affects the core rendering engine of the browser, meaning that any webpage containing maliciously crafted text elements could serve as an attack vector, making it extremely difficult to defend against through traditional content filtering approaches.
The exploitation of this vulnerability demonstrates techniques that align with ATT&CK framework's T1059.007 sub-technique for command and scripting interpreter, as successful exploitation would likely involve crafting payloads that manipulate memory structures to achieve code execution. The memory corruption aspect also relates to T1068, which covers local privilege escalation through process manipulation. Organizations should prioritize immediate patching of affected versions, as the vulnerability's potential for remote code execution makes it a high-priority threat. Mitigation strategies beyond patching should include implementing web application firewalls, restricting access to potentially malicious content, and monitoring for suspicious memory access patterns in browser processes. The vulnerability serves as a reminder of the critical importance of memory safety in browser implementations and the need for robust code review processes to prevent such flaws in complex software systems.