CVE-2026-92039 Mozilla CVE debrief

Who should care

Defenders responsible for managing Firefox, Firefox ESR, and Thunderbird deployments, especially in environments where user interaction with notifications is common, should assess exposure and apply patches.

Why it matters

CVE-2026-92039 is a medium-severity mitigation bypass vulnerability in the DOM: Notifications component of Firefox, Firefox ESR, and Thunderbird. Defenders should prioritize verifying exposure and applying patches, especially in environments where user interaction with notifications is common. The vulnerability's impact is limited to the affected software versions, and its exploitation requires user interaction.

• Verification of exposure and patch application for Firefox, Firefox ESR, and Thunderbird
• Monitoring for suspicious activity related to notifications
• Inventory checks for affected software versions

Technical summary

The CVE-2026-92039 vulnerability involves a mitigation bypass in the DOM: Notifications component of Firefox, Firefox ESR, and Thunderbird. This issue was addressed in Firefox 156, Firefox ESR 153.3, Thunderbird 156, and Thunderbird 153.3. The vulnerability's CVSS score is 6.3, indicating a medium severity level. The vulnerability allows attackers to bypass existing mitigations, potentially leading to further exploitation. Defenders should prioritize verifying exposure and applying patches, especially in environments where user interaction with notifications is common.

Defensive priority

Defenders should prioritize verifying exposure and applying patches for Firefox, Firefox ESR, and Thunderbird, especially in environments where user interaction with notifications is common.

Recommended defensive actions

• Verify and apply patches for Firefox, Firefox ESR, and Thunderbird
• Inventory systems for exposure to the affected components
• Monitor for suspicious activity related to notifications
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD entry provide details on the vulnerability and affected software versions. Mozilla's security advisories (MFSA 2026-90, MFSA 2026-93, MFSA 2026-94, MFSA 2026-96) offer additional information on the vulnerability and patches.

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.