CVE-2026-92047: Firefox Privilege Escalation Vulnerability

CVE-2026-92047 Overview

CVE-2026-92047 is a privilege escalation vulnerability in the Crash Reporting component of Mozilla Firefox and Thunderbird. Mozilla addressed the flaw in Firefox 156, Firefox ESR 153.3, Thunderbird 156, and Thunderbird 153.3. The weakness maps to [CWE-269] Improper Privilege Management. An attacker exploiting this issue could gain elevated privileges through the crash reporter workflow after user interaction with a malicious page or content.

Critical Impact
Successful exploitation allows privilege escalation with high impact to confidentiality, integrity, and availability, requiring only limited user interaction over a network attack vector.

Affected Products

Mozilla Firefox versions prior to 156
Mozilla Firefox ESR versions prior to 153.3
Mozilla Thunderbird versions prior to 156 and 153.3

Discovery Timeline

2026-09-15 - CVE-2026-92047 published to NVD
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-92047

Vulnerability Analysis

The vulnerability resides in the Crash Reporting component shared across Firefox and Thunderbird. The Crash Reporter is a privileged helper that collects diagnostic information after a browser or mail client crash. Improper privilege management within this component allows a lower-privileged context to obtain higher privileges than intended. Because the crash reporter interacts with sensitive process state, an escalation here can affect confidentiality, integrity, and availability of the host environment.

Root Cause

The root cause is classified under [CWE-269] Improper Privilege Management. The component fails to properly constrain the privileges granted during crash-handling operations. This allows actions that should require elevated authorization to be performed from a less-trusted context. Mozilla resolved the flaw through updates to the crash reporter privilege boundary in the fixed releases.

Attack Vector

Exploitation requires network-reachable content and user interaction, consistent with typical browser-driven attack chains. An attacker crafts content that triggers or manipulates the crash reporting workflow to abuse the improperly managed privilege boundary. See the Mozilla Bug Report #2059021 and the Mozilla Security Advisory MFSA-2026-90 for vendor details.

No verified public proof-of-concept code is available for this vulnerability. Refer to the vendor advisories for authoritative technical context.

Detection Methods for CVE-2026-92047

Indicators of Compromise

Unexpected execution of the Firefox or Thunderbird crash reporter process (crashreporter.exe on Windows, crashreporter on Linux/macOS) outside of legitimate crash events.
Creation of new privileged processes or child processes spawned by the browser or mail client immediately following a crash event.
Anomalous file writes or registry modifications performed under the security context of the crash reporter.

Detection Strategies

Monitor endpoint telemetry for parent-child process relationships where firefox.exe or thunderbird.exe spawns crash reporter processes followed by additional privileged child processes.
Alert on unexpected privilege transitions or token elevation associated with Mozilla application processes.
Correlate browser crash events with subsequent suspicious command-line activity or persistence artifacts on the same host.

Monitoring Recommendations

Inventory Firefox and Thunderbird versions across the environment and flag hosts running versions prior to Firefox 156, Firefox ESR 153.3, or Thunderbird 156/153.3.
Enable process command-line and integrity-level logging on endpoints to surface abnormal crash reporter behavior.
Review Mozilla advisories MFSA-2026-93, MFSA-2026-94, and MFSA-2026-96 for related fixes bundled in the same release cycle.

How to Mitigate CVE-2026-92047

Immediate Actions Required

Update Firefox to version 156 or later on all managed endpoints.
Update Firefox ESR deployments to version 153.3 or later.
Update Thunderbird to version 156 or Thunderbird ESR 153.3 or later.
Verify update deployment status through software inventory tools and remediate hosts that remain on vulnerable builds.

Patch Information

Mozilla published fixes in Firefox 156, Firefox ESR 153.3, Thunderbird 156, and Thunderbird 153.3. Consult the Mozilla Security Advisory MFSA-2026-90 and related advisories MFSA-2026-93, MFSA-2026-94, and MFSA-2026-96 for release notes and affected build identifiers.

Workarounds

No official vendor workaround is documented; apply the vendor patches as the primary remediation path.
Restrict user ability to install or downgrade Firefox and Thunderbird through endpoint policy to prevent regression to vulnerable versions.
Enforce least-privilege user accounts to limit the blast radius of any successful privilege escalation attempt.