CVE-2026-117914 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the SVG 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 • 10/27/2026
The identified vulnerability represents a critical memory management error classified as an out-of-bounds write resulting from a use-after-free condition within the Scalable Vector Graphics rendering engine of Mozilla Firefox browsers. This specific flaw occurs when the application continues to reference a block of memory that has already been deallocated by the system, leading to undefined behavior during the parsing and rendering of SVG content. Such vulnerabilities are typically categorized under CWE-416 in the Common Weakness Enumeration framework, which highlights the danger of accessing freed memory regions without proper validation or reallocation checks. The root cause often stems from complex event handling sequences where an object is destroyed while still being referenced by another active component within the browser's rendering pipeline, particularly when processing dynamically generated or maliciously crafted SVG files that trigger specific cleanup routines prematurely.
From a technical perspective, this use-after-free scenario allows for arbitrary code execution with the privileges of the target process if exploited successfully. An attacker can construct a specially designed HTML page containing an SVG element that manipulates memory allocation and deallocation patterns to achieve heap corruption. By carefully controlling the contents written into the freed memory region through subsequent allocations, it is possible to overwrite function pointers or object vtables. This mechanism aligns with ATT&CK technique T1203, which involves exploitation for client-side code execution, as well as techniques related to browser-based attacks such as those found in MITRE ATT&CK ID TA0004 under the Impact and Execution tactics. The severity of this vulnerability is heightened by its potential to bypass modern memory protection mechanisms like ASLR and DEP if the heap layout can be precisely controlled through multiple allocation cycles, a process often referred to as heap grooming.
The operational impact of this flaw extends beyond simple application crashes or denial-of-service conditions, although those are immediate symptoms for users encountering malformed SVG content. The primary risk lies in remote code execution capabilities that enable attackers to install malware, steal sensitive data such as cookies and session tokens, or establish persistent access on the victim's system. Since Firefox is widely used across enterprise environments and general consumer markets, a successful exploit could serve as an initial vector for broader network intrusions. Users accessing untrusted web content, including phishing sites or compromised advertising networks that inject malicious SVG payloads, are at significant risk. The vulnerability affects multiple versions of the browser, indicating a systemic issue in the core rendering logic rather than an isolated edge case, thereby increasing the attack surface across different user demographics and operational contexts.
Mitigation strategies primarily involve immediate software updates to incorporate the fixes released by Mozilla Corporation. Administrators should ensure that all instances of Firefox are upgraded to version 159 or later for standard releases, while enterprise environments relying on extended support must apply patch level 115.44 for ESR 115 and 153.6 for ESR 153. These updates contain the necessary code changes to validate memory pointers before access and ensure proper lifecycle management of SVG objects during rendering operations. In addition to updating software, organizations should implement strict content security policies that restrict the execution of inline scripts and limit the types of resources loaded from external domains. Deploying browser isolation technologies or sandboxed browsing profiles can further reduce the impact by limiting the privileges granted to any potential exploit attempts. Regular vulnerability scanning and patch management cycles are essential to maintain a secure posture against such memory corruption vulnerabilities, which remain among the most prevalent threats in modern web browsers.