CVE-2012-5840 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the nsTextEditorState::PrepareEditor 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, a different vulnerability than CVE-2012-4214.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 04/19/2021
The CVE-2012-5840 vulnerability represents a critical use-after-free condition within Mozilla Firefox's text editor state management component, specifically in the nsTextEditorState::PrepareEditor function. This flaw exists in multiple Mozilla products including Firefox, Thunderbird, and SeaMonkey across various versions, making it particularly dangerous as it affects a widely used browser and email client ecosystem. The vulnerability stems from improper memory management where freed memory blocks are still being accessed or referenced, creating opportunities for malicious exploitation. The issue is categorized under CWE-416, which specifically addresses use-after-free vulnerabilities, and falls into the broader category of heap memory corruption flaws that can lead to arbitrary code execution or system instability.
The technical implementation of this vulnerability occurs when the nsTextEditorState::PrepareEditor function handles text editor state transitions, particularly during operations involving text manipulation and editing contexts. When certain text processing operations are performed, the function may free memory resources associated with text editor state objects while other code paths continue to reference those freed memory locations. This memory management error creates a scenario where attackers can manipulate the application's memory layout to execute malicious code with the privileges of the running browser process. The vulnerability differs from CVE-2012-4214 in its specific code path and memory access patterns, yet shares similar exploitation principles related to heap corruption.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to include full remote code execution capabilities, making it a severe threat to user systems. Attackers can craft malicious web pages or email content that, when processed by vulnerable applications, triggers the use-after-free condition and allows arbitrary code execution on the target system. The heap memory corruption can be leveraged to overwrite critical memory structures, redirect program execution flow, or inject malicious payloads. This vulnerability particularly affects users who frequently interact with web content or email messages, as the attack vectors can be delivered through standard web browsing or email client operations. The exploitation typically requires user interaction with malicious content, making social engineering a significant factor in successful attacks.
Mitigation strategies for CVE-2012-5840 primarily involve immediate patching of affected software versions, with users urged to upgrade to Firefox 17.0, Thunderbird 17.0, and SeaMonkey 2.14 or their respective ESR versions. System administrators should prioritize deployment of security updates across all affected platforms, as the vulnerability can be exploited remotely without user interaction in certain scenarios. Additional protective measures include implementing browser security restrictions, disabling unnecessary plugins, and employing content filtering solutions to prevent access to potentially malicious websites. The vulnerability demonstrates the importance of memory safety practices in software development, particularly in applications handling user-generated content, and aligns with ATT&CK techniques related to code injection and privilege escalation. Organizations should also consider implementing security monitoring to detect potential exploitation attempts and maintain updated threat intelligence regarding similar memory corruption vulnerabilities.