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CVE-2026-16369 Mozilla CVE debrief

CVE-2026-16369 is an integer overflow vulnerability in the JavaScript: WebAssembly component. The issue was addressed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13. This vulnerability has a CVSS score of 9.8 and is considered CRITICAL. Users of affected products should apply patches immediately to prevent exploitation.

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

Users of Firefox, Firefox ESR, Thunderbird, and Thunderbird 140.13 should apply the patches to prevent exploitation of this vulnerability. This includes administrators and users of these products in managed environments.

Technical summary

The CVE-2026-16369 vulnerability is caused by an integer overflow in the JavaScript: WebAssembly component. This issue was patched in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13. The vulnerability has a high impact on confidentiality, integrity, and availability, affecting users of these products in managed environments. Users should update their browsers to the latest versions to mitigate this vulnerability. Administrators and users of Firefox, Firefox ESR, Thunderbird, and Thunderbird 140.13 should apply patches immediately to prevent exploitation. Further verification is recommended based on the CVE record and NVD entry.

Defensive priority

High

Recommended defensive actions

  • Apply patches for Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13
  • Ensure all users are running the latest version of their browser
  • Monitor for any suspicious activity related to this vulnerability
  • 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 was published on 2026-07-21T13:17:06.707Z and was last modified on 2026-07-22T20:16:53.427Z. The NVD entry is currently Undergoing Analysis. This information is based on the CVE record and NVD entry. Further verification is recommended.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-16369 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-16369

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

  • CVE-2026-16369 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-16369

    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.