CVE-2026-84131 in Firefox
Summary
by MITRE • 09/01/2026
Privilege escalation due to invalid pointer in the Graphics component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, and Firefox ESR 153.2.
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Analysis
by VulDB Data Team • 09/01/2026
The identified security flaw represents a critical privilege escalation vector located within the graphics subsystem of Mozilla Firefox browsers. This vulnerability stems from an invalid pointer dereference condition that occurs during the processing of graphical data structures. In complex rendering engines, memory management is handled through intricate allocation and deallocation routines where pointers serve as references to specific locations in system memory. When these pointers are not properly validated or initialized before being used for read or write operations, they may reference unmapped memory regions, corrupted heap segments, or arbitrary addresses controlled by an attacker. This type of flaw falls squarely under the Common Weakness Enumeration category CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer and often relates to CWE-416 Use After Free if the pointer references memory that has already been released back to the system allocator.
The operational impact of this vulnerability is severe because it allows an attacker who can trick a user into visiting a specially crafted webpage or loading malicious content with complex graphics instructions to execute arbitrary code within the context of the browser process. By exploiting the invalid pointer, an adversary can achieve out-of-bounds read access to gather sensitive information such as cookies, session tokens, or cached credentials stored in memory. More critically, through techniques like heap spraying combined with precise control over the invalid pointer value, it is possible to overwrite function pointers or return addresses on the stack. This leads to arbitrary code execution, effectively granting the attacker full control over the browser process and potentially facilitating further lateral movement within a user's environment if sandboxing mechanisms are bypassed or misconfigured.
From an offensive security perspective, this vulnerability aligns with several tactics in the MITRE ATT&CK framework for enterprise environments. It is primarily associated with T1059 Command and Scripting Interpreter through the execution of injected code payloads, as well as T1203 Exploitation for Client Execution where malicious content triggers local software vulnerabilities to gain initial access. The exploitation chain typically involves crafting a WebGL or Canvas-based exploit that manipulates GPU driver interactions or internal graphics API calls within Firefox’s rendering pipeline. Successful exploitation requires the victim to interact with the malicious site, making social engineering elements often part of the broader attack campaign alongside this technical flaw.
Mitigation strategies for this vulnerability rely heavily on timely patching and defense-in-depth measures. The primary remediation is upgrading Mozilla Firefox to version 155 or later, as well as updating all supported Extended Support Release channels including ESR versions 115.40, 140.15, and 153.2 which contain the specific code fixes for this pointer validation issue. Organizations should enforce automated update policies to ensure that browser instances are kept current with security patches released by Mozilla. Additionally, enabling strict content security policies and disabling unnecessary JavaScript features on untrusted sites can reduce the attack surface available to exploiters attempting to trigger these graphics-related memory corruption bugs. Security teams should also monitor for indicators of compromise related to unusual process behavior or network connections originating from browser processes following visits to high-risk web destinations.