CVE-2016-5261 in Firefox
Summary
by MITRE
Integer overflow in the WebSocketChannel class in the WebSockets subsystem in Mozilla Firefox before 48.0 and Firefox ESR < 45.4 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via crafted packets that trigger incorrect buffer-resize operations during buffering.
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Analysis
by VulDB Data Team • 09/09/2022
The vulnerability CVE-2016-5261 represents a critical integer overflow flaw within the WebSocketChannel class of Mozilla Firefox's WebSockets subsystem. This issue affects Firefox versions prior to 48.0 and Firefox ESR versions before 45.4, creating a significant security risk that can be exploited by remote attackers to execute arbitrary code or cause denial of service conditions. The vulnerability stems from improper handling of buffer resize operations during WebSocket packet processing, where integer overflow conditions lead to memory corruption that can be leveraged for code execution.
The technical flaw manifests when crafted malicious WebSocket packets are processed by the affected Firefox versions, specifically within the WebSocketChannel class implementation. During the buffering process, the system performs operations that involve integer arithmetic to determine buffer sizes, but fails to properly validate or handle cases where integer overflow occurs. This overflow results in incorrect buffer allocation sizes that can cause memory corruption, potentially allowing attackers to overwrite adjacent memory locations or manipulate heap structures. The vulnerability aligns with CWE-190, which specifically addresses integer overflow conditions that can lead to memory corruption and arbitrary code execution. The flaw represents a classic buffer overflow scenario where the system allocates insufficient memory due to miscalculated integer values, creating opportunities for attackers to inject malicious code or cause system instability.
The operational impact of this vulnerability extends beyond simple denial of service to encompass full remote code execution capabilities. Attackers can craft specially designed WebSocket packets that, when processed by vulnerable Firefox instances, trigger the integer overflow condition and subsequently corrupt memory structures. This memory corruption can be exploited to overwrite critical program variables, function pointers, or return addresses, enabling attackers to redirect execution flow and ultimately execute arbitrary code with the privileges of the affected browser process. The vulnerability can be particularly dangerous in web environments where users may unknowingly connect to malicious WebSocket servers, as the exploitation can occur without user interaction beyond visiting a compromised website. This aligns with ATT&CK technique T1059.007 for command and script interpreter, where attackers can leverage the compromised browser to execute malicious code through the WebSocket channel.
Mitigation strategies for CVE-2016-5261 primarily focus on immediate version upgrades to Firefox 48.0 or later, or Firefox ESR 45.4 and later releases where the vulnerability has been patched. Organizations should implement comprehensive patch management processes to ensure all affected Firefox installations are updated promptly, as the vulnerability can be exploited remotely without user interaction. Additional defensive measures include network-level controls such as WebSocket traffic filtering and monitoring for suspicious packet patterns, though these are less effective than proper patching. The vulnerability demonstrates the importance of proper input validation and integer overflow protection in network protocol implementations, particularly in browser-based systems where memory safety is paramount. Security teams should also consider implementing browser hardening measures and monitoring for unusual WebSocket traffic patterns that might indicate exploitation attempts, as the integer overflow condition can manifest in various forms of memory corruption that may not immediately result in visible system crashes but can be leveraged for persistent attacks.