CVE-2026-92056 in Firefox
Summary
by MITRE • 09/15/2026
Use-after-free in the Graphics: Text component. This vulnerability was fixed in Firefox 156 and Firefox ESR 153.3.
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Analysis
by VulDB Data Team • 09/15/2026
The identified vulnerability represents a critical memory management error classified as an out-of-bounds write, specifically manifesting as a use-after-free condition within the text rendering subsystem of the browser engine. This flaw occurs when the application attempts to access or modify memory that has already been deallocated by the system's garbage collector or explicit free operations. In the context of web browsers, such errors are particularly dangerous because they allow an attacker who controls the input data to influence how the browser handles memory pointers after those resources have been released. The Graphics: Text component is responsible for laying out and rendering textual content on screen, a process that involves complex interactions between layout engines, font renderers, and display buffers. When this subsystem fails to properly validate pointer validity before accessing freed memory regions, it creates an opportunity for arbitrary code execution or denial of service attacks against the end user.
From a technical perspective, use-after-free vulnerabilities arise when a program continues to use a pointer after the memory it points to has been reclaimed. This can happen due to logic errors in reference counting mechanisms or race conditions where multiple threads access shared resources without proper synchronization. In browser environments, these flaws are often triggered by specific sequences of DOM manipulation events combined with CSS styling rules that force reflows and repaints. An attacker could craft a malicious webpage containing specially designed HTML and JavaScript code that exploits this timing gap. By triggering the deallocation of text-related objects while maintaining references to them elsewhere in the application state, the attacker can cause the browser to write data into unintended memory locations. This arbitrary write capability is significant because it allows for overwriting function pointers or object vtables, which are common techniques used to hijack control flow and execute malicious payloads with the privileges of the victim process.
The operational impact of this vulnerability extends beyond simple application crashes, although denial of service remains a likely outcome if exploitation fails. Successful exploitation could lead to remote code execution on the user's machine, granting attackers full access to sensitive data stored locally or enabling further lateral movement within a network environment. Given that browsers are often used as gateways for accessing corporate resources and personal accounts, compromising the browser process can serve as an initial foothold for broader cyberattacks. The vulnerability affects both standard releases of Firefox version 156 and the Extended Support Release (ESR) branch at version 153.3, indicating that it was present in stable builds used by a significant portion of users who prioritize stability over frequent feature updates. This widespread exposure increases the attack surface available to threat actors targeting enterprise environments or individual consumers relying on these specific versions for their daily browsing activities.
Industry standards provide clear frameworks for understanding and mitigating such risks. The Common Weakness Enumeration (CWE) categorizes this issue under CWE-416, which defines use-after-free errors as a distinct class of memory safety violations. Additionally, the MITRE ATT&CK framework maps exploitation techniques involving browser vulnerabilities to tactics like Initial Access via Spearphishing Attachment or Drive-by Compromise, where malicious content is delivered through compromised websites or phishing campaigns. To mitigate these risks, organizations should prioritize patch management strategies that ensure timely deployment of security updates provided by software vendors. For users unable to update immediately due to compatibility concerns with legacy systems, implementing network-level controls such as web filtering proxies can help block access to known malicious domains hosting exploit kits. Furthermore, enabling sandboxing features and restricting JavaScript permissions in browser settings can reduce the impact of successful exploitation attempts by limiting the scope of actions a compromised page can perform within the operating system environment.