CVE-2026-92029 in Firefox
Summary
by MITRE • 09/15/2026
Use-after-free in the SVG component. This vulnerability was fixed in Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, and Firefox ESR 153.3.
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Analysis
by VulDB Data Team • 09/15/2026
The identified security flaw represents a critical use-after-free condition within the Scalable Vector Graphics rendering engine of Mozilla Firefox browsers. This type of vulnerability arises when memory that has been deallocated is subsequently accessed by the application logic without proper validation or reallocation checks. In the specific context of SVG processing, this typically occurs during the complex lifecycle management of graphical objects where elements are dynamically created, modified, and destroyed in response to user interaction or script execution. When an object reference persists after its underlying memory has been freed due to a race condition, logic error, or improper state transition, any subsequent attempt to read from or write to that dangling pointer results in undefined behavior within the browser process.
From a technical perspective, use-after-free vulnerabilities are particularly dangerous because they allow attackers to manipulate heap metadata and arbitrary memory locations with high precision. By carefully crafting malicious SVG content containing specific sequences of element creation and removal, an attacker can control what data resides at the freed memory address before it is accessed again. This capability enables the overwriting of function pointers or object vtables, which serves as a direct pathway to achieve arbitrary code execution on the victim's system. The exploitability of this flaw relies heavily on heap grooming techniques designed to place sensitive structures in predictable locations within the browser’s memory space, thereby increasing the reliability and success rate of the attack chain against modern mitigation technologies such as Address Space Layout Randomization and Heap Protection mechanisms.
The operational impact of this vulnerability is severe, potentially leading to complete compromise of the user's system integrity. If successfully exploited, an attacker could execute arbitrary code with the privileges of the browser process, which often includes access to local files, network credentials stored in cookies or history, and sensitive session tokens. This can facilitate further lateral movement within a corporate network if the victim is part of an enterprise environment using Firefox as their primary web client. The risk is exacerbated by the fact that SVG content can be embedded directly into HTML pages via iframe tags or data URIs, meaning users do not need to visit a dedicated malicious site but could trigger the exploit simply by loading a compromised webpage containing the crafted vector graphics payload.
Industry standards classify this flaw under CWE-416, which defines use-after-free as a category of memory corruption vulnerabilities where software continues to use pointers after they have been freed. In terms of offensive security frameworks such as MITRE ATT&CK, this vulnerability aligns with techniques related to Initial Access via Spearphishing Link or Drive-by Code Execution, specifically leveraging browser-based exploits for code execution. The exploitation vector falls under the broader category of Client-Side Attacks where the target is tricked into executing malicious content through a trusted application like a web browser. Understanding these classifications helps security teams prioritize patching efforts and implement appropriate detection rules based on known exploit patterns associated with heap corruption in rendering engines.
Mitigation strategies primarily focus on timely deployment of vendor-supplied patches, as this issue has been resolved in Firefox version 156, Firefox Extended Support Release versions 115.41, 140.16, and 153.3. Organizations should enforce automated update policies to ensure all endpoints are running the latest secure builds of the browser. Additionally, implementing strict Content Security Policy headers can help mitigate some risks by restricting the sources from which scripts and resources are loaded, although this does not directly prevent exploitation through native SVG rendering flaws. For environments where immediate patching is not feasible, network-level filtering solutions that inspect HTTP traffic for known malicious payloads or anomalous behavior patterns associated with browser exploit kits may provide a layer of defense in depth against active threats targeting this specific vulnerability class.