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PatchSiren cyber security CVE debrief

CVE-2026-8954 Mozilla CVE debrief

CVE-2026-8954 is a HIGH-severity Mozilla vulnerability in the Audio/Video component involving incorrect boundary conditions and an integer overflow (CWE-119). NVD rates it 7.5 with a network-reachable, no-auth, no-interaction CVSS vector, and Mozilla says it is fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

Vendor
Mozilla
Product
Firefox
CVSS
HIGH 7.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-19
Original CVE updated
2026-05-19
Advisory published
2026-05-19
Advisory updated
2026-05-19

Who should care

Firefox and Thunderbird users, endpoint-management teams, browser and desktop administrators, and security operations staff should care. Prioritize systems running Firefox versions below 151, Firefox ESR below 140.11, and Thunderbird installations that have not yet been updated to the Mozilla-fixed releases.

Technical summary

The source record describes an Audio/Video component flaw caused by incorrect boundary conditions and an integer overflow. NVD maps the weakness to CWE-119 and assigns CVSS 3.1 vector AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N, indicating low-complexity exploitation with confidentiality impact and no privileges or user interaction required. Mozilla-linked advisories state the issue is fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

Defensive priority

High. The issue is rated 7.5/HIGH, is network-reachable, and requires neither privileges nor user interaction per the CVSS vector. Patch priority should be elevated for managed Firefox and Thunderbird fleets, especially where updates lag behind Mozilla's fixed releases.

Recommended defensive actions

  • Update Firefox to 151 or later, or Firefox ESR to 140.11 or later.
  • Update Thunderbird to 151 or later, or to the Mozilla-fixed 140.11 release line where applicable.
  • Inventory endpoints to identify any Mozilla browser/mail clients still below the fixed versions.
  • Verify automatic update mechanisms and force remediation on managed devices that cannot self-update promptly.

Evidence notes

This debrief is based on the official NVD CVE record and Mozilla-linked references in the supplied corpus. NVD provides the severity, CVSS vector, CWE mapping, and vulnerable CPE criteria, while Mozilla advisories and Bugzilla issue 2030747 are referenced as vendor sources. No exploit details or proof-of-concept material are included in the supplied source set.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-8954 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-8954

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

  • CVE-2026-8954 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-8954

    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.