CVE-2026-92049 Mozilla CVE debrief

Who should care

Defenders responsible for Firefox, Firefox ESR, Thunderbird, and Thunderbird 153.3 deployments should assess exposure and prioritize upgrades to patched versions. This includes reviewing the vulnerability details, assessing the potential impact on their organization, and planning the necessary upgrades or mitigations. Additionally, defenders should review the Mozilla security advisories for additional details and verify exposure in their deployments.

Why it matters

A use-after-free vulnerability in the Widget: Win32 component of Firefox, Firefox ESR, Thunderbird, and Thunderbird 153.3 was fixed in Firefox 156, Firefox ESR 153.3, Thunderbird 156, and Thunderbird 153.3. Defenders should prioritize verifying exposure in their deployments and assess upgrade feasibility to patched versions.

• Verify exposure in Firefox, Firefox ESR, Thunderbird, and Thunderbird 153.3 deployments
• Assess upgrade feasibility to patched versions (Firefox 156, Firefox ESR 153.3, Thunderbird 156, and Thunderbird 153.3)
• Review Mozilla security advisories for additional details

Technical summary

The CVE record describes a use-after-free vulnerability in the Widget: Win32 component of Firefox, Firefox ESR, Thunderbird, and Thunderbird 153.3. The vulnerability was fixed in Firefox 156, Firefox ESR 153.3, Thunderbird 156, and Thunderbird 153.3. The vulnerability affects the Widget: Win32 component, which is used in Firefox, Firefox ESR, Thunderbird, and Thunderbird 153.3. The vulnerability was reported by an external researcher and is a use-after-free issue. The Mozilla security advisories (MFSA2026-90, MFSA2026-93, MFSA2026-94, and MFSA2026-96) may contain additional details.

Defensive priority

Defenders should prioritize verifying exposure in their Firefox, Firefox ESR, Thunderbird, and Thunderbird 153.3 deployments and assess upgrade feasibility to patched versions.

Recommended defensive actions

• Verify exposure in Firefox, Firefox ESR, Thunderbird, and Thunderbird 153.3 deployments
• Assess upgrade feasibility to patched versions (Firefox 156, Firefox ESR 153.3, Thunderbird 156, and Thunderbird 153.3)
• Review Mozilla security advisories for additional details
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The CVE record and NVD entry provide limited information about the vulnerability. The Mozilla security advisories (MFSA2026-90, MFSA2026-93, MFSA2026-94, and MFSA2026-96) may contain additional details.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.