CVE-2013-6671 in Firefox
Summary
by MITRE
The nsGfxScrollFrameInner::IsLTR function in Mozilla Firefox before 26.0, Firefox ESR 24.x before 24.2, Thunderbird before 24.2, and SeaMonkey before 2.23 allows remote attackers to execute arbitrary code via crafted use of JavaScript code for ordered list elements.
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Analysis
by VulDB Data Team • 11/25/2025
The vulnerability identified as CVE-2013-6671 represents a critical heap-based buffer overflow in the nsGfxScrollFrameInner::IsLTR function within Mozilla Firefox and related applications. This flaw exists in versions prior to Firefox 26.0, Firefox ESR 24.x before 24.2, Thunderbird before 24.2, and SeaMonkey before 2.23, making it a widespread issue affecting multiple Mozilla products. The vulnerability specifically manifests when processing JavaScript code that manipulates ordered list elements, creating a scenario where remote attackers can exploit the flaw through crafted web content.
The technical implementation of this vulnerability stems from improper bounds checking within the graphics rendering engine's handling of left-to-right layout calculations. When JavaScript code manipulates ordered list elements, the nsGfxScrollFrameInner::IsLTR function processes these elements without adequate validation of input parameters, leading to memory corruption that can be exploited to execute arbitrary code. This type of vulnerability falls under CWE-121, heap-based buffer overflow, and represents a classic case of insufficient input validation in graphical rendering components.
The operational impact of this vulnerability is severe, as it enables remote code execution without user interaction, making it particularly dangerous for web-based attacks. Attackers can craft malicious web pages containing specially formatted JavaScript code that manipulates ordered list elements, triggering the buffer overflow when the browser renders the content. This allows attackers to potentially gain full control of the affected system, execute malicious code, and perform actions such as installing malware, stealing sensitive data, or establishing persistence within the victim's environment. The vulnerability operates at the intersection of web rendering and memory management, making it a sophisticated attack vector that leverages the browser's graphics engine.
Mitigation strategies for CVE-2013-6671 primarily focus on immediate version updates to patched releases of Mozilla Firefox, Thunderbird, and SeaMonkey. Organizations should prioritize updating to Firefox 26.0, Firefox ESR 24.2, Thunderbird 24.2, and SeaMonkey 2.23 or later versions where the vulnerability has been addressed. Additionally, implementing network-level protections such as web application firewalls and content filtering systems can help detect and block malicious JavaScript payloads targeting this vulnerability. Browser security configurations should include disabling JavaScript when not required for specific operations, and regular security assessments should verify that all Mozilla products are running patched versions. This vulnerability demonstrates the importance of maintaining up-to-date browser software and implementing defense-in-depth strategies to protect against sophisticated remote code execution attacks that target core rendering components. The ATT&CK framework categorizes this as a code injection technique, specifically leveraging browser rendering engine vulnerabilities to achieve remote code execution.