CVE-2026-117927 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 use-after-free conditions within the Scalable Vector Graphics rendering engine of Mozilla Firefox browsers. This specific flaw occurs when the application attempts to access or manipulate memory that has already been deallocated, leading to undefined behavior and potential exploitation by malicious actors. The vulnerability was addressed in recent security updates for Firefox version 159 as well as extended support releases including ESR versions 115.44 and 153.6, indicating a significant effort to remediate memory corruption issues that could compromise browser stability and user data integrity.
From a technical perspective, use-after-free vulnerabilities arise when pointers continue to reference freed memory blocks after the operating system has returned those resources for reuse. In the context of SVG processing, this typically involves complex object lifecycles where DOM elements are removed or replaced while asynchronous operations or event handlers still hold references to them. When such stale references are dereferenced, they may point to newly allocated data structures that serve different purposes than originally intended. This mismatch allows attackers to craft maliciously designed SVG files containing specific sequences of events and element manipulations that trigger the premature deallocation followed by immediate access, thereby gaining control over memory layout or executing arbitrary code through heap spraying techniques.
The operational impact of this vulnerability is severe due to its potential for remote code execution without user interaction beyond visiting a compromised website. Attackers can leverage this flaw to bypass modern browser security mitigations such as sandboxing and data execution prevention by achieving precise memory writes that alter control flow instructions or overwrite function pointers within the rendering process. This capability enables full system compromise if combined with other vulnerabilities, although standalone exploitation remains challenging due to advanced heap hardening measures implemented in recent Firefox versions. Nevertheless, successful exploitation could lead to unauthorized access to sensitive information stored locally on the victim's machine including cookies, saved passwords, and browsing history associated with the compromised profile.
Industry standards categorize this type of flaw under CWE-416 which denotes use after free scenarios that result in unpredictable behavior or security breaches. Additionally, related attack patterns align with MITRE ATT&CK techniques involving memory corruption exploitation often seen in drive-by download campaigns where malicious content is served via web pages rather than direct file downloads. The presence of such vulnerabilities highlights the importance of rigorous static analysis and fuzzing during software development particularly for components handling untrusted input like SVG parsers which process complex graphical data structures from external sources.
Mitigation strategies primarily involve applying the provided patches to update affected browser versions immediately upon release. Organizations should enforce automated patch management policies ensuring that all endpoints running Firefox are updated within defined service level agreements to minimize exposure windows. For environments where immediate updating is not feasible, network-level filtering can be employed to block access to known malicious domains hosting exploit kits or suspicious SVG content until patches are deployed. Users must remain vigilant against phishing attempts designed to trick them into visiting compromised sites and should disable JavaScript execution for untrusted sources using browser extensions as an additional layer of defense though this approach significantly degrades user experience and is not recommended as a primary security control.
Further hardening measures include enabling all available memory protection features such as ASLR DEP and sandboxing which reduce the likelihood that successful exploitation leads to full system compromise. Regular vulnerability scanning and penetration testing should incorporate checks for similar memory corruption issues in other browser components beyond just SVG rendering engines since these flaws often indicate broader weaknesses in object lifecycle management across multiple modules within large codebases like Gecko engine used by Firefox developers must prioritize secure coding practices emphasizing proper reference counting smart pointers and RAII patterns to prevent dangling pointer scenarios during dynamic resource allocation phases.