CVE-2026-117999 in Firefox
Summary
by MITRE • 10/27/2026
Race condition in the IPC component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/27/2026
The identified security issue represents a race condition within the Inter-Process Communication (IPC) subsystem of Mozilla Firefox, specifically affecting versions prior to 159 for standard releases and prior to version 153.6 for Extended Support Release channels. Race conditions in IPC mechanisms are particularly critical because they involve synchronization failures between distinct operating system processes that share memory or communicate via message passing. In the context of browser architecture, where multiple tabs, extensions, and background services operate as separate processes to isolate content from privileged code, a race condition can allow an attacker to manipulate the timing of these interactions in ways that bypass intended security checks. This vulnerability highlights a flaw in how state transitions are managed during concurrent access to shared resources within the IPC layer, potentially leading to undefined behavior or privilege escalation scenarios if exploited effectively by malicious web content.
From a technical perspective, race conditions typically arise when two or more threads or processes attempt to read and write data concurrently without proper synchronization primitives such as mutexes, semaphores, or atomic operations ensuring exclusive access during critical sections. In Firefox's IPC implementation, this could manifest in scenarios where the order of message processing is not strictly enforced under high concurrency, allowing a maliciously crafted webpage to trigger specific sequences of events that exploit timing windows. For instance, an attacker might attempt to perform an action before a security check has completed or after it has been bypassed due to state inconsistency. Such vulnerabilities are often difficult to detect through static analysis alone and require sophisticated fuzzing techniques or dynamic instrumentation to reproduce the precise timing conditions necessary for exploitation. The presence of this flaw indicates that certain code paths within the IPC handler did not adequately guard against concurrent modifications, creating an opportunity for unauthorized data access or execution flow manipulation.
The operational impact of this vulnerability is significant due to its potential to compromise the browser's security model. If successfully exploited, a race condition in the IPC component could allow a remote attacker executing malicious JavaScript on a compromised webpage to escalate privileges within the browser process space. This might lead to arbitrary code execution with the permissions of the user running the browser, facilitating data theft such as session cookies, saved passwords, or sensitive form inputs. Furthermore, it could enable sandbox escape scenarios where an attacker breaks out of the restricted content process into more privileged processes like the main browser process or utility processes handling downloads and updates. The severity is compounded by the fact that IPC vulnerabilities are often targeted in drive-by download attacks or malicious ad networks, making them a high-value target for threat actors seeking to establish persistent access on victim systems without requiring user interaction beyond visiting a webpage.
To mitigate this risk, users must ensure their browsers are updated to Firefox version 159 or later, and ESR users should update to version 153.6 or higher immediately upon availability. These updates contain the necessary code changes that enforce proper synchronization mechanisms within the IPC layer, eliminating the timing window exploited by attackers. In environments where immediate patching is not feasible due to compatibility testing requirements, network-level controls such as web application firewalls can be configured to block known malicious payloads associated with exploiting race conditions in browser components. Additionally, enabling strict Content Security Policy headers and disabling unnecessary extensions can reduce the attack surface available to potential exploiters. It is also advisable for organizations to monitor for indicators of compromise related to unusual process behavior or unexpected network connections originating from Firefox processes, which may signal an active exploitation attempt targeting this vulnerability class.
This incident aligns with common weakness enumerations such as CWE-362, which defines race conditions involving concurrent access and updates to a shared resource where the final outcome depends on the sequence or timing of other events. It also relates to ATT&CK technique T1059, Command and Scripting Interpreter, if the exploitation leads to arbitrary code execution, and potentially T1078, Valid Accounts, if it results in unauthorized access to user sessions. Understanding these mappings helps security teams prioritize remediation efforts based on established threat intelligence frameworks. The resolution of this issue underscores the importance of rigorous testing for concurrency bugs in complex software architectures like modern web browsers, where IPC is a fundamental component ensuring both performance and isolation. Continuous integration pipelines should include dynamic analysis tools capable of detecting race conditions to prevent similar defects from reaching production releases in future updates.