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CVE-2026-16379 Mozilla CVE debrief

CVE-2026-16379 is a critical vulnerability in the DOM: Content Processes component of Firefox, Firefox ESR, Thunderbird, and Thunderbird 140.13. The vulnerability allows for privilege escalation and was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13. The CVSS score for this vulnerability is 9.8, indicating a high severity level. Users of these products should update to the latest versions to mitigate the vulnerability. The vulnerability's impact is likely significant due to its critical severity and the wide range of affected products.

Vendor
Mozilla
Product
Firefox
CVSS
CRITICAL 9.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-21
Original CVE updated
2026-07-22
Advisory published
2026-07-21
Advisory updated
2026-07-22

Who should care

This vulnerability affects users of Firefox, Firefox ESR, Thunderbird, and Thunderbird 140.13. Users of these products should update to the latest versions to mitigate the vulnerability. Additionally, security teams and vulnerability management teams should review the official advisories and assess their exposure to this vulnerability.

Technical summary

The vulnerability is a privilege escalation issue in the DOM: Content Processes component. It was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13. The CVSS vector for this vulnerability is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. This vulnerability affects users of Firefox, Firefox ESR, Thunderbird, and Thunderbird 140.13, and users should update to the latest versions to mitigate the vulnerability.

Defensive priority

High

Recommended defensive actions

  • Update Firefox to version 153 or later
  • Update Firefox ESR to version 140.13 or later
  • Update Thunderbird to version 153 or later
  • Update Thunderbird to version 140.13 or later
  • 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

Evidence notes

The vulnerability was reported by [email protected]. The CVE record was published on 2026-07-21T13:17:13.067Z and modified on 2026-07-22T20:16:55.057Z. Evidence is limited to public sources and may not reflect the full scope or impact of the vulnerability. Defenders should verify affected systems and review official advisories for specific guidance.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-16379 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-16379

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

  • CVE-2026-16379 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-16379

    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.