CVE-2026-16381 is a vulnerability in Mozilla Firefox's Networking: DNS component that allows bypassing the same-origin policy. The same-origin policy is a fundamental browser security mechanism that restricts how documents or scripts loaded from one origin can interact with resources from another origin. This vulnerability could allow an attacker to circumvent these restrictions. Mozilla fixed this issue in Firefox 153 and Firefox ESR 140.13. The vendor advisory categorizes the impact as moderate and no active exploitation is known. The advisory is part of a broader security update addressing multiple vulnerabilities.

The vulnerability enables bypassing the same-origin policy in the DNS networking component, potentially allowing unauthorized access to resources across origins. This can lead to security issues such as unauthorized data access or manipulation within the browser context. However, no known exploits in the wild have been reported, and the vendor rates the impact as moderate.

Mozilla has released official fixes for this vulnerability in Firefox 153 and Firefox ESR 140.13. Users and administrators should update affected Firefox installations to these versions or later to remediate the vulnerability. Since the vulnerability is fixed in these versions, no additional mitigation steps are required beyond applying the update.