CVE-2015-0813 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the AppendElements function in Mozilla Firefox before 37.0, Firefox ESR 31.x before 31.6, and Thunderbird before 31.6 on Linux, when the Fluendo MP3 plugin for GStreamer is used, allows remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption) via a crafted MP3 file.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 11/25/2025
The CVE-2015-0813 vulnerability represents a critical use-after-free flaw in Mozilla Firefox and Thunderbird applications that specifically impacts systems utilizing the Fluendo MP3 plugin for GStreamer. This vulnerability exists within the AppendElements function of the affected software versions, creating a dangerous condition where memory previously freed by the application is accessed again. The flaw is particularly concerning because it can be exploited remotely through maliciously crafted MP3 files, making it a significant threat to user security and system stability.
The technical nature of this vulnerability stems from improper memory management within the multimedia processing pipeline of the affected browsers. When the Fluendo MP3 plugin processes audio files, it interacts with Firefox's internal memory structures through the AppendElements function. Under normal circumstances, this function should properly manage memory allocation and deallocation. However, the vulnerability occurs when the plugin encounters malformed MP3 content that triggers a race condition or improper memory handling, leading to a scenario where freed memory blocks are accessed again by subsequent operations. This use-after-free condition creates heap memory corruption that can be leveraged by attackers to execute arbitrary code or cause system crashes.
The operational impact of CVE-2015-0813 extends beyond simple denial of service to potentially enable full system compromise. Attackers can craft MP3 files that, when played through the affected browsers, trigger the memory corruption vulnerability. This allows for remote code execution with the privileges of the compromised user, potentially leading to complete system takeover. The vulnerability is particularly dangerous because it affects both Firefox and Thunderbird applications, which are widely used for web browsing and email operations. The Linux-specific nature of the issue indicates that the memory management characteristics of the Linux operating system, combined with the GStreamer plugin architecture, create conditions that make this exploit more likely to succeed.
The vulnerability aligns with CWE-416, which describes use-after-free conditions, and represents a classic example of heap corruption vulnerabilities that have been consistently exploited in browser security research. From an attack framework perspective, this vulnerability maps to several ATT&CK techniques including initial access through malicious file delivery, privilege escalation via code execution, and persistence mechanisms that could be established through successful exploitation. The Fluendo MP3 plugin component adds complexity to the attack surface since it introduces additional memory management layers and plugin-specific code paths that may not be fully protected against memory safety issues. Organizations using affected versions of Firefox or Thunderbird are at significant risk, particularly in environments where users may encounter untrusted audio content, making this vulnerability particularly relevant for enterprise security teams and system administrators who must maintain up-to-date browser installations to protect against such remote exploitation vectors.
Mitigation strategies for CVE-2015-0813 primarily focus on immediate version upgrades to patched releases of Firefox, Firefox ESR, and Thunderbird. System administrators should prioritize deployment of security patches from Mozilla, as these updates contain fixes for the memory management issues in the AppendElements function. Additionally, organizations should consider implementing content filtering measures to prevent execution of untrusted MP3 files, though this approach is less effective than patching since the vulnerability can be triggered through legitimate audio files. Network-based protections such as web application firewalls and sandboxing mechanisms can provide additional defense-in-depth, though they may not completely prevent exploitation of this memory corruption vulnerability. Regular security assessments and vulnerability scanning should be conducted to ensure all systems remain protected against similar memory safety issues that may arise in multimedia processing components.