CVE-2026-92015 Mozilla CVE debrief

Who should care

Defenders responsible for managing Firefox and Thunderbird deployments should assess exposure and prioritize remediation. This includes IT administrators, security teams, and developers working with WebExtensions.

Why it matters

CVE-2026-92015 is a high-severity privilege escalation vulnerability in Firefox's WebExtensions component. Defenders must verify affected versions, apply updates, and monitor for exploitation attempts. The vulnerability was fixed in multiple Firefox and Thunderbird updates.

• Defenders must verify affected versions and apply updates to prevent potential exploitation.
• Successful exploitation could lead to privilege escalation, allowing attackers to gain elevated access.
• Remediation priority is high due to the vulnerability's severity and potential impact.
• Further verification is needed to determine the full scope of affected systems and potential consequences.

Technical summary

The CVE-2026-92015 vulnerability is a high-severity privilege escalation issue in the WebExtensions component of Firefox. It affects multiple versions of Firefox and Thunderbird, including Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, Firefox ESR 153.3, Thunderbird 156, Thunderbird 140.16, and Thunderbird 153.3. The vulnerability has a CVSS score of 8.8 and is considered HIGH severity. Defenders should prioritize verifying affected Firefox and Thunderbird versions, applying updates, and monitoring for potential exploitation attempts.

Defensive priority

Defenders should prioritize verifying affected Firefox and Thunderbird versions, applying updates, and monitoring for potential exploitation attempts.

Recommended defensive actions

• Verify affected Firefox and Thunderbird versions
• Apply updates to vulnerable systems
• Monitor for potential exploitation attempts
• 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, including its CVSS score of 8.8 and affected versions. Vendor advisories from Mozilla offer additional context and mitigation guidance. Defenders should verify affected Firefox and Thunderbird versions, apply updates, and monitor for potential exploitation attempts. The vulnerability was fixed in Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, Firefox ESR 153.3, Thunderbird 156, Thunderbird 140.16, and Thunderbird 153.3.

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.