CVE-2026-117913 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the SVG component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/27/2026
The identified security flaw represents a critical memory management error classified as an out-of-bounds write, specifically manifesting as a use-after-free condition within the Scalable Vector Graphics rendering engine of Mozilla Firefox browsers. This vulnerability arises from improper handling of object lifecycles during the parsing and layout phases of SVG content processing. When the browser processes complex or malformed SVG documents, it may retain references to memory structures that have already been deallocated by the garbage collector or explicit cleanup routines. Subsequent operations attempting to access these dangling pointers result in writes to invalid memory locations, which can corrupt adjacent heap data or overwrite critical control structures within the application's memory space.
From a technical perspective, this flaw aligns with Common Weakness Enumeration identifier CWE-416, use after free, and is frequently associated with CWE-787 out-of-bounds write when the dereferenced pointer leads to writing beyond allocated boundaries. The attack vector typically involves an attacker crafting a malicious SVG file or embedding such content within a web page that triggers specific rendering paths in the browser engine. By carefully manipulating DOM elements and CSS properties, an adversary can force the application into a state where memory is freed while still being referenced by active layout objects. This scenario allows for arbitrary code execution if the overwritten data includes function pointers or object vtables, effectively bypassing modern exploit mitigations such as ASLR and DEP under certain conditions.
The operational impact of this vulnerability is severe, potentially leading to remote code execution on vulnerable systems without user interaction beyond visiting a compromised website. Attackers could leverage this flaw to install malware, steal sensitive data, or establish persistent access within the victim's environment. Given that Firefox serves as a primary browser for many enterprise and personal users, widespread exploitation could result in significant compromise of individual privacy and organizational security postures. The vulnerability was addressed in Mozilla Firefox version 159 and Firefox Extended Support Release version 153.6 through rigorous code reviews and the implementation of additional bounds checking mechanisms within the SVG parsing logic to ensure that memory references are validated before access occurs.
Mitigation strategies primarily involve ensuring all instances of affected software are updated to the patched versions immediately upon availability. For organizations unable to patch instantly, network-level filtering can be employed to block traffic containing suspiciously crafted SVG payloads or restrict execution of untrusted scripts within browser contexts. Additionally, enabling strict Content Security Policy headers and disabling JavaScript in low-trust environments can reduce the attack surface by preventing the exploitation chain from completing its final stages. Continuous monitoring for anomalous memory behavior and deploying endpoint detection solutions that flag unusual heap activity can provide supplementary defense-in-depth measures against this class of vulnerabilities.