CVE-2026-92037: Firefox DOM Animation Boundary Vulnerability

CVE-2026-92037 Overview

CVE-2026-92037 is a boundary condition vulnerability in the DOM: Animation component of Mozilla Firefox and Thunderbird. Mozilla addressed the flaw in Firefox 156 and Thunderbird 156. The issue affects how the Animation component enforces boundary conditions when processing web content, which could lead to unexpected memory or state handling behavior in the browser engine.

The vulnerability was disclosed through Mozilla Foundation Security Advisories MFSA-2026-90 and MFSA-2026-94, with underlying technical details tracked in Mozilla Bug Report #2068460.

Critical Impact
A boundary condition error in the DOM: Animation component may allow attacker-controlled web content to trigger out-of-bounds behavior in Firefox and Thunderbird versions prior to 156.

Affected Products

Mozilla Firefox versions prior to 156
Mozilla Thunderbird versions prior to 156
Downstream distributions bundling affected Firefox or Thunderbird builds

Discovery Timeline

2026-09-15 - CVE-2026-92037 published to NVD
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-92037

Vulnerability Analysis

The flaw resides in the DOM: Animation component, which is responsible for handling Web Animations API operations inside the Gecko engine. Mozilla describes the issue as an incorrect boundary conditions error. Such errors typically arise when code fails to correctly validate index ranges, buffer offsets, or timing boundaries before performing an operation on animation-related data structures.

When the Animation component processes attacker-influenced input, a miscalculated boundary can lead to memory access outside intended bounds or to inconsistent internal state. Mozilla shipped fixes in Firefox 156 and Thunderbird 156 to correct the boundary logic in the affected code paths.

The EPSS model currently reflects low expected exploitation activity, and no public proof-of-concept or in-the-wild exploitation has been reported at time of publication.

Root Cause

The root cause is an incorrect boundary condition inside the DOM: Animation implementation. Full technical specifics are restricted in Bugzilla #2068460 pending broad patch adoption, per Mozilla's standard disclosure practice.

Attack Vector

Exploitation would require a victim to load attacker-controlled web content in an unpatched Firefox build or to render remote content in an unpatched Thunderbird client. No authentication is required, and the attack surface is reachable through standard web navigation or HTML email rendering. Specific exploitation prerequisites and impact class have not been publicly disclosed by Mozilla.

No verified exploitation code is available. Refer to the Mozilla Security Advisory MFSA-2026-90 for authoritative technical context.

Detection Methods for CVE-2026-92037

Indicators of Compromise

No public indicators of compromise have been published for CVE-2026-92037.
Presence of Firefox or Thunderbird builds with version numbers below 156 in the environment.
Browser or mail client crash reports referencing the Animation or Web Animations subsystem.

Detection Strategies

Inventory installed Firefox and Thunderbird versions across managed endpoints and flag any build earlier than 156.
Monitor endpoint telemetry for unexpected child process launches or memory faults originating from firefox.exe or thunderbird.exe.
Correlate web proxy logs with reports of anomalous browser behavior on hosts running unpatched versions.

Monitoring Recommendations

Enable crash reporting and forward Gecko crash signatures to a centralized log platform for review.
Track vendor advisory feeds from Mozilla for updates to MFSA-2026-90 and MFSA-2026-94.
Alert on installation or persistence of outdated Firefox or Thunderbird packages after patch deployment cycles.

How to Mitigate CVE-2026-92037

Immediate Actions Required

Upgrade Mozilla Firefox to version 156 or later on all managed endpoints.
Upgrade Mozilla Thunderbird to version 156 or later on all managed endpoints.
Validate that Extended Support Release (ESR) channels, if in use, have received the corresponding backported fix.

Patch Information

Mozilla resolved CVE-2026-92037 in Firefox 156 and Thunderbird 156. Consult MFSA-2026-90 and MFSA-2026-94 for the complete list of fixed builds and channel-specific guidance.

Workarounds

Disable JavaScript execution for untrusted origins where operationally feasible until patches are deployed.
Render Thunderbird messages in plain-text mode to reduce exposure of the DOM: Animation code path via HTML email.
Restrict browsing on unpatched hosts to trusted internal resources through proxy allow-listing.

bash

# Verify installed Firefox version on Linux endpoints
firefox --version

# Verify installed Thunderbird version on Linux endpoints
thunderbird --version

# Example: enforce plain-text mail rendering in Thunderbird user.js
# user_pref("mailnews.display.prefer_plaintext", true);
# user_pref("mailnews.display.html_as", 1);