CVE-2026-74949 in Firefox
Summary
by MITRE • 08/18/2026
Privilege escalation due to use-after-free in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.
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Analysis
by VulDB Data Team • 08/18/2026
The identified security flaw resides within the Graphics subsystem of Mozilla Firefox, specifically targeting the Canvas2D rendering engine which is responsible for handling two-dimensional drawing operations on web pages via HTML5 canvas elements. This vulnerability manifests as a use-after-free error, a critical memory corruption issue where the application continues to reference a block of memory after it has been freed or deallocated by the system. In the context of browser-based attacks, such flaws are particularly dangerous because they allow an attacker who controls the content of a webpage to manipulate how the browser interprets data in memory, potentially leading to arbitrary code execution with the privileges of the user running the application.
From a technical perspective, use-after-free vulnerabilities typically arise when object lifetime management is not strictly enforced during dynamic rendering processes. In this case, the Canvas2D component likely failed to properly invalidate references or update pointers after releasing resources associated with canvas operations. When an attacker crafts a malicious webpage that triggers specific drawing commands or state changes, they can cause the browser to free certain graphics objects while retaining active references to them. Subsequent access to these dangling pointers allows for reading from or writing to arbitrary memory locations, bypassing standard security boundaries and enabling privilege escalation within the sandboxed environment of the browser process.
The operational impact of this vulnerability is severe, as it facilitates remote code execution without requiring any user interaction beyond visiting a maliciously crafted website. Attackers can leverage this flaw to execute arbitrary commands on the victim's system, install malware, steal sensitive data such as cookies and session tokens, or pivot further into internal networks if the browser has broader access rights. The absence of robust memory safety checks in older versions of Firefox meant that exploitation could occur reliably across various operating systems supported by the browser, making it a high-priority target for automated exploit kits distributed through compromised websites or phishing campaigns.
Industry standards classify this type of vulnerability under CWE-416, which denotes Use After Free conditions where pointers are not properly managed leading to undefined behavior and potential security breaches. Furthermore, in terms of attack tactics, this flaw aligns with MITRE ATT&CK techniques related to memory corruption exploitation, specifically those that bypass sandbox restrictions through arbitrary read/write primitives derived from heap or stack manipulation. The ability to escalate privileges within the browser process is a critical step for attackers aiming to achieve full system compromise, as it breaks the isolation model designed to contain web content execution.
To mitigate this risk, organizations and individual users must ensure that Mozilla Firefox is updated to version 154, Firefox ESR 140.14, or Firefox ESR 153.1 at minimum. These releases incorporate patches that correct the memory management logic within the Canvas2D component, ensuring that references are properly nullified and objects are correctly tracked throughout their lifecycle during rendering operations. Additionally, deploying browser hardening solutions such as content security policies, sandboxing technologies like Google Chrome Frame or equivalent modern containerization methods for web viewing, and keeping all system dependencies up to date can provide layered defense against exploitation attempts. Regular vulnerability scanning and monitoring of threat intelligence feeds are also recommended to detect any emerging exploits targeting this specific component before they are widely deployed in the wild.