Description

Privilege escalation in the Memory component. This vulnerability was fixed in Firefox 156 and Firefox ESR 153.3.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-09-15T13:16:58.800Z",
  "pubdate": "2026-09-15T13:16:58.800Z",
  "executiveSummary": "This vulnerability involves a critical flaw within the memory management subsystem of the Firefox browser, allowing for local privilege escalation.\nThe vulnerability resides in the Memory component, which manages the allocation, deallocation, and lifecycle of process memory segments.\nSuccessful exploitation permits an attacker, who has already gained restricted access to the system, to elevate their privileges to a higher security context within the Firefox environment.\nThis may enable unauthorized access to sensitive user data, credential caches, or further system-level compromise by bypassing standard memory protection mechanisms.\nThe flaw affects both standard Firefox and the Extended Support Release (ESR) channels.\nExploitation requires the attacker to successfully trigger specific memory state inconsistencies, potentially involving race conditions or use-after-free scenarios that manipulate memory pointers.\nDue to the nature of privilege escalation, this vulnerability poses a significant risk to the integrity and confidentiality of the browser session and the underlying host operating system.\nUsers are strongly urged to update to the specified patched versions to mitigate potential threats.",
  "technicalDetails": "The vulnerability is situated within the Firefox Memory component, specifically targeting the logic governing how memory regions are handled during complex state transitions. The root cause is identified as an improper validation or synchronization issue during the handling of memory objects, which may lead to an exploitable memory corruption state.\nIn a typical attack flow, the adversary must interact with the memory management subsystem through controlled input, such as specifically crafted web content or malicious script execution that forces the browser to perform unexpected memory operations. By inducing a state where the memory manager incorrectly references a deallocated object or an invalid memory address (Use-After-Free or Pointer Confusion), the attacker gains the ability to manipulate internal data structures.\nOnce the attacker successfully triggers the memory inconsistency, they can gain arbitrary read/write primitives within the context of the Firefox process. This allows for the overwriting of function pointers, object metadata, or security tokens that the browser relies upon to verify user privileges. By redirecting the instruction pointer or modifying sensitive control-flow data, the attacker can hijack execution flow.\nThe privilege escalation aspect is achieved when the attacker elevates the process's internal security capabilities, effectively breaking out of the browser's sandbox or moving from a low-privileged content process to a higher-privileged browser process. This bypasses the Principle of Least Privilege, granting the attacker access to browser internal APIs, system files, or sensitive persistent data that are usually protected by the sandbox architecture.\nThis vulnerability affects Firefox versions prior to 156 and Firefox ESR versions prior to 153.3. There is no requirement for remote authentication, though the exploit usually requires an entry vector via malicious web pages or compromised extensions to trigger the vulnerable memory operations. The complexity of the exploit relies on the attacker's ability to maintain stable heap spray or state synchronization in the face of existing memory protection technologies like Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP)."
}