CVE-2026-92027 Mozilla CVE debrief

Who should care

Defenders responsible for managing Firefox, Firefox ESR, and Thunderbird installations should assess exposure and prioritize patching for high-risk systems. This includes IT administrators, security teams, and vulnerability management teams who need to ensure that affected systems are updated and secured. Additionally, defenders should review and update incident response plans to address potential exploitation and conduct vulnerability scanning to identify

Why it matters

CVE-2026-92027 is a high-severity use-after-free vulnerability in Firefox, Firefox ESR, and Thunderbird. Defenders should prioritize patching and verifying system exposure.

• Verify and apply patches to prevent potential exploitation
• Inventory and update outdated versions of Firefox, Firefox ESR, and Thunderbird
• Monitor for potential exploitation attempts
• Consider implementing compensating controls for high-risk exposures

Technical summary

The CVE-2026-92027 vulnerability is a use-after-free issue in the DOM: Streams component of Firefox, Firefox ESR, and Thunderbird. This vulnerability has been addressed in 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 could potentially allow attackers to execute arbitrary code or cause a denial-of-service condition. Defenders should prioritize verifying and applying patches for affected systems, particularly for users with high-risk exposure.

Defensive priority

Defenders should prioritize verifying and applying patches for affected systems, particularly for users with high-risk exposure, such as those using older versions of Firefox, Firefox ESR, and Thunderbird.

Recommended defensive actions

• Verify and apply patches for affected Firefox, Firefox ESR, and Thunderbird installations
• Inventory systems for outdated versions of Firefox, Firefox ESR, and Thunderbird
• Monitor for potential exploitation attempts
• Consider implementing compensating controls for high-risk exposures
• Review and update incident response plans to address potential exploitation
• Conduct vulnerability scanning to identify exposed systems
• Implement additional security measures for high-risk exposures

Evidence notes

The CVE record and NVD vulnerability detail page provide information on the vulnerability, including its CVSS score and vector. Mozilla security advisories (MFSA) provide additional context and mitigation guidance.

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.