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PatchSiren cyber security CVE debrief

CVE-2026-6760 Mozilla CVE debrief

A critical vulnerability, CVE-2026-6760, was found in the Networking: Cookies component of Firefox and Thunderbird. This mitigation bypass issue was fixed in Firefox 150 and Thunderbird 150. The vulnerability has a CVSS score of 9.8 and is considered critical. Defenders should assess exposure and apply necessary updates. The issue allows attackers to bypass mitigations, making it critical to address. The CVE record and NVD vulnerability detail page provide information on the vulnerability, including its CVSS score and affected versions.

Vendor
Mozilla
Product
Firefox
CVSS
CRITICAL 9.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-21
Original CVE updated
2026-10-26
Advisory published
2026-04-21
Advisory updated
2026-10-26

Who should care

Defenders responsible for managing Firefox and Thunderbird installations should assess exposure and apply necessary updates. This vulnerability could potentially allow attackers to bypass mitigations, making it critical to address.

Why it matters

CVE-2026-6760 is a critical mitigation bypass vulnerability in Firefox and Thunderbird that requires immediate attention from defenders. It has a CVSS score of 9.8 and was fixed in Firefox 150 and Thunderbird 150.

  • Defenders need to verify if their systems are using Firefox or Thunderbird versions prior to 150.
  • This vulnerability could potentially allow attackers to bypass mitigations, making it critical to address.
  • Defenders should prioritize applying updates to Firefox 150 and Thunderbird 150.

Technical summary

The CVE-2026-6760 vulnerability is a critical mitigation bypass issue in the Networking: Cookies component of Firefox and Thunderbird. It was fixed in Firefox 150 and Thunderbird 150. The vulnerability has a CVSS score of 9.8, indicating a high severity level.

Defensive priority

Defenders should prioritize verifying if their systems are using Firefox or Thunderbird versions prior to 150 and apply the necessary updates. This is a critical vulnerability that could potentially allow attackers to bypass mitigations.

Recommended defensive actions

  • Verify if Firefox or Thunderbird versions prior to 150 are in use and apply updates.
  • Review system configurations to ensure mitigations are in place.
  • Monitor for potential exploitation attempts.

Evidence notes

The CVE record and NVD vulnerability detail page provide information on the vulnerability, including its CVSS score and affected versions. Vendor advisories are also available, detailing the fixes in Firefox 150 and Thunderbird 150.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-6760 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-6760

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-6760 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-6760

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental 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.