Description

Concurrent execution using shared resource with improper synchronization ('race condition') in Microsoft Edge (Chromium-based) allows an authorized attacker to elevate privileges locally.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-09-14T18:20:19.343Z",
  "pubdate": "2026-09-14T18:20:19.343Z",
  "executiveSummary": "This vulnerability is classified as a race condition, specifically identified as a concurrent execution issue involving shared resources with improper synchronization within Microsoft Edge (Chromium-based).\nThe security flaw facilitates a local privilege escalation, permitting an authorized, authenticated user to achieve higher levels of system access than originally granted.\nThe defect resides within the underlying Chromium architectural implementation, which impacts the integrity of resource management during multi-threaded operations.\nThe risk implication is significant as it undermines the security boundaries maintained by the browser process model, potentially allowing a malicious actor to escape sandboxed environments or gain escalated execution context.\nSuccessful exploitation requires the attacker to have local access to the affected system. By leveraging precise timing in concurrent resource access, an attacker can trigger non-deterministic behavior to manipulate shared memory or object states.\nAs this is a local privilege escalation vector, it does not rely on network exposure, making it a critical concern for multi-user environments or systems where local account security is paramount.",
  "technicalDetails": "The vulnerability originates from inadequate synchronization primitives when multiple threads within the Chromium-based architecture attempt to access or mutate a shared resource simultaneously. In complex browser environments, multiple asynchronous operations, such as IPC (Inter-Process Communication) message handling, DOM modifications, or garbage collection cycles, frequently compete for shared memory structures.\nA race condition occurs when the system's security posture is dependent on the sequence or timing of uncontrollable events. In this instance, the improper synchronization creates a 'Time-of-Check to Time-of-Use' (TOCTOU) window. An attacker can influence the state of the system during this ephemeral interval.\nThe exploitation flow typically begins with the attacker establishing a local foothold within the system. They then manipulate the execution environment to cause contention on the vulnerable resource. By flooding the application with requests or specific process activities, the attacker increases the probability of the race condition manifesting during the window where the resource is either being validated or utilized.\nIf the thread synchronization fails, the application may inadvertently operate on an inconsistent state or a partially initialized object. This can lead to memory corruption, such as Use-After-Free (UAF) or double-free conditions, which are common manifestations of underlying race conditions. By carefully crafting the timing of these concurrent operations, the attacker can force the browser process to execute code or access privileged APIs with the security token of a more privileged process or the parent system process.\nThe vulnerable component is likely deep within the Chromium core, specifically within the browser's multi-process isolation architecture or the resource management layer. Because Microsoft Edge inherits the Chromium codebase, vulnerabilities related to race conditions often involve the bridge between the renderer process (the sandboxed environment) and the browser process (which manages system-level interactions).\nExploitation requires the attacker to be authenticated on the local machine. There is no remote network exposure component inherent to this specific vulnerability. Upon successful exploitation, the attacker achieves privilege escalation, potentially breaking out of the browser sandbox to execute arbitrary commands with higher privileges, such as the current user's full context or administrative rights, depending on the process integrity level of the target component."
}