CVE-2026-16379: Mozilla Firefox privilege escalation in DOM Content Processes

Executive brief

A privilege escalation vulnerability was identified in the Firefox web browser's content process management. This flaw could allow a malicious website to gain higher-level permissions within the browser than intended, potentially bypassing security boundaries. If successfully exploited, an attacker could gain unauthorized access to browser functions or data that should be restricted to the system level.

Technical details

A privilege escalation vulnerability exists in the Mozilla Firefox 'DOM: Content Processes' component. The flaw allows for a breach of process isolation boundaries, potentially enabling a compromised content process to escalate its privileges within the browser architecture. The vulnerability is reachable via web content (network vector) and requires no specific user interaction beyond visiting a malicious site. Mozilla has addressed this issue in Firefox 153 and Firefox ESR 140.13.

Affected products

• Mozilla Firefox < 153
• Mozilla Firefox ESR < 140.13

Timeline

• 2026-07-21: advisory
• 2026-07-21: patched

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=2039452
• https://www.mozilla.org/security/advisories/mfsa2026-68/
• https://www.mozilla.org/security/advisories/mfsa2026-70/