Description

Sandbox escape due to use-after-free in the Preferences: Backend component. This vulnerability was fixed in Firefox 157.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.6",
  "pubDate": "2026-09-29T13:17:45.493Z",
  "pubdate": "2026-09-29T13:17:45.493Z",
  "executiveSummary": "A critical memory corruption vulnerability exists within the Preferences: Backend component of the Firefox browser, manifesting as a use-after-free (UAF) condition.\nThe flaw enables a sophisticated sandbox escape, potentially allowing an attacker to break out of the browser's restricted security environment.\nBy leveraging this vulnerability, a remote attacker could execute arbitrary code with elevated privileges, bypassing the sandbox protections that typically isolate web content from the underlying operating system.\nThis vulnerability affects Firefox versions prior to 157.\nThe risk implication is severe, as it facilitates full compromise of the user's browser session and potentially the host system if combined with further exploitation primitives.\nSuccessful exploitation requires the attacker to influence the browser's internal state to trigger the dangling pointer, which may be achieved via maliciously crafted web content.\nThe flaw represents a significant security breakdown in the process isolation architecture of the Firefox browser.",
  "technicalDetails": "The vulnerability is rooted in a use-after-free (UAF) condition within the Preferences: Backend component of Firefox. This class of memory safety error occurs when the application fails to properly manage the lifecycle of an object, leading to a pointer referencing a memory location after the object residing there has been deallocated.\nIn the context of the Preferences: Backend, this typically involves a race condition or an improper reference count during object destruction. If a reference to a preferences-related object is cached by a component or callback, and that object is subsequently freed—for instance, during a configuration change or synchronization event—the remaining pointer becomes a dangling pointer.\nThe exploitation flow begins with an attacker inducing the browser to allocate a specific object within the preferences subsystem. Through crafted JavaScript interactions or malicious UI-triggering events, the attacker coerces the browser to free the memory associated with that object while retaining a reference to it.\nOnce the memory has been freed, the attacker performs heap grooming or memory spraying to reallocate the specific address space with attacker-controlled data. When the browser subsequently attempts to access the dangling pointer, it inadvertently interacts with the malicious payload injected into the heap.\nBy carefully crafting the layout of the sprayed memory, an attacker can manipulate the internal structure of the Preferences component. If the object contains virtual function pointers (vtable) or other functional pointers, the attacker can overwrite them to redirect the execution flow to arbitrary code, such as a ROP (Return Oriented Programming) chain.\nThis execution happens within the context of the browser process. In the case of a sandbox escape, the attacker leverages this arbitrary code execution primitive to gain control over the browser process's capabilities. Because the Preferences component often interacts with higher-privileged or IPC-bridging mechanisms, the transition from a compromised content process to the broader system environment becomes feasible.\nThis vulnerability does not require authentication, as it is triggered through standard browser interaction with web content. It relies on the browser's internal memory management failures, making it a critical threat to user privacy and system integrity."
}