CVE-2026-117863 in Firefox
Summary
by MITRE • 10/27/2026
Information disclosure due to uninitialized memory in the Audio/Video component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/28/2026
The identified security flaw represents a critical class of vulnerabilities known as information disclosure via uninitialized memory within the browser's Audio/Video processing subsystem. This specific issue arises when software components allocate or reference memory blocks that have not been properly initialized with default values before being accessed by subsequent operations. In complex multimedia frameworks, such as those handling audio and video streams in web browsers, data buffers are frequently reused to optimize performance. If a buffer is reallocated without clearing its previous contents, residual data from prior sessions or unrelated processes may remain within the memory space. When this uninitialized memory is subsequently read or exposed through application interfaces, it can inadvertently leak sensitive information that was previously stored there but not overwritten by new valid data.
From a technical perspective, this vulnerability aligns with Common Weakness Enumeration category CWE-457, which describes the use of an uninitialized variable. The root cause typically involves logic errors in memory management routines where developers assume that allocated memory is zeroed out or explicitly initialize it before first use. In the context of Firefox's media pipeline, such a flaw could allow maliciously crafted web content to trigger specific code paths that read from these uninitialized regions. This might result in the exposure of internal browser state, cryptographic keys, session tokens, or other private data structures that were previously held in those memory locations but are no longer actively used for their original purpose. The lack of proper initialization creates a predictable yet unintended side channel through which an attacker can extract confidential information without directly exploiting buffer overflows or code execution flaws.
The operational impact of this vulnerability is primarily centered on confidentiality rather than integrity or availability. An attacker who successfully exploits this flaw could potentially gain access to sensitive user data that should remain isolated within the browser's secure environment. This might include details about other open tabs, cached credentials, or internal configuration settings that aid in further reconnaissance against the victim system. While direct remote code execution is not implied by an uninitialized memory read alone, such information disclosure often serves as a precursor step in more complex attack chains. By understanding the internal state of the browser through leaked data, attackers can refine subsequent exploits to achieve higher-impact outcomes, making this vulnerability a significant risk factor for overall system security posture.
This type of flaw is frequently associated with ATT&CK technique T1005, which covers Data from Local System Retrieval via non-Credential-based methods like memory scraping or reading sensitive files and directories. The exploitation vector typically involves malicious web content that triggers the vulnerable code path through standard browser APIs related to media playback or processing. To mitigate this risk, it is essential for developers to enforce strict initialization practices across all memory allocation routines within critical subsystems such as audio and video handling. Static analysis tools and dynamic fuzzing should be employed during development to detect instances where variables are used before being assigned a value. Furthermore, runtime protections like Address Sanitizer can help identify these issues in testing environments before they reach production builds.
The resolution of this vulnerability was implemented in Firefox version 159 as well as the Extended Support Release versions 115.44 and 153.6. Users are strongly advised to update their browsers immediately to ensure that the patched code paths are active, thereby eliminating the possibility of uninitialized memory being exposed through media processing functions. Regular updates remain the most effective defense against such low-level software defects, as they incorporate rigorous security patches developed by vendor engineering teams who have analyzed and corrected the underlying logic errors responsible for these information leaks.