CVE-2026-117874 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the Internationalization 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 vulnerability represents a critical memory management error classified as an out-of-bounds write resulting from use-after-free conditions within the Internationalization component of Mozilla Firefox. This specific flaw occurs when the application attempts to access or manipulate memory that has already been deallocated by the system, leading to undefined behavior and potential exploitation scenarios. The root cause typically involves a mismatch in reference counting or lifecycle management where an object is freed while still being referenced by other parts of the codebase, particularly during complex text processing operations handled by the internationalization subsystem which manages locale-specific formatting and string manipulation.
From a technical perspective, use-after-free vulnerabilities are among the most dangerous classes of memory corruption bugs because they allow attackers to control what data resides in the freed memory region before it is reallocated for another purpose. In the context of Firefox's Internationalization component, this could involve manipulating how text encoding or locale settings are processed during rendering or input handling. When an attacker can trigger a sequence that causes premature deallocation followed by access, they may achieve arbitrary code execution with the privileges of the user running the browser. This is particularly severe because it bypasses many modern memory safety protections if the freed memory is quickly reused for sensitive structures such as function pointers or object headers.
The operational impact of this vulnerability extends beyond simple application crashes to include potential remote code execution through maliciously crafted web content. An attacker could design a specially constructed webpage that exploits the race condition or logic error in the internationalization handling routines, causing Firefox to execute arbitrary commands on the victim's machine. This compromises the integrity and confidentiality of user data, as well as potentially allowing further lateral movement within a network if the browser is used for internal applications or sensitive transactions. The severity is amplified by the widespread adoption of Firefox across enterprise environments where users may have elevated privileges or access to critical systems.
Mitigation strategies primarily involve applying the vendor-provided patches immediately upon release. For organizations relying on extended support releases, it is crucial to monitor updates for Firefox ESR versions 153.6 and 115.44 specifically, as these contain the necessary fixes for this memory corruption issue. Additionally, implementing strict content security policies can help mitigate some exploitation vectors by restricting how scripts interact with browser internals. Security teams should also ensure that all instances of Firefox are updated to version 159 or later where applicable, ensuring that the underlying memory management logic in the internationalization module is corrected and no longer susceptible to these use-after-free conditions.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-416 which describes Use After Free scenarios. It also maps to MITRE ATT&CK techniques related to initial access via browser exploitation, specifically leveraging software vulnerabilities for remote code execution. Understanding this mapping helps security professionals prioritize patching efforts and configure detection rules in endpoint protection platforms that monitor for suspicious memory allocation patterns or unusual process behavior indicative of such exploits being attempted against the internationalization subsystems of web browsers.