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CVE-2026-16408 Mozilla CVE debrief

CVE-2026-16408 is an integer overflow vulnerability in the Audio/Video: Playback component of Firefox and Thunderbird. This vulnerability was fixed in Firefox 153 and Thunderbird 153. The vulnerability has a CVSS score of 9.8, indicating a critical severity. Users of Firefox and Thunderbird should apply the patches to prevent exploitation of this vulnerability. The vulnerability allows attackers to potentially execute arbitrary code.

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 and Thunderbird should apply the patches to prevent exploitation of this vulnerability. This includes users of Firefox and Thunderbird who have not updated to the latest versions. Security teams and vulnerability management teams should also be aware of this vulnerability and take necessary actions to protect their assets.

Technical summary

The vulnerability is caused by an integer overflow in the Audio/Video: Playback component of Firefox and Thunderbird. The CVSS score is 9.8, indicating a critical severity. The vulnerability was fixed in Firefox 153 and Thunderbird 153. The vulnerability affects users of Firefox and Thunderbird who have not updated to the latest versions. Defensive measures include applying patches and monitoring for suspicious activity.

Defensive priority

High

Recommended defensive actions

  • Apply patches for Firefox 153 and Thunderbird 153
  • Ensure that Firefox and Thunderbird are updated to the latest versions
  • 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 2026-07-21T13:17:16.220Z and was last modified on 2026-07-22T20:16:59.847Z. The NVD entry is currently Modified. This information is based on the CVE.org and NVD sources. The vulnerability affects Firefox and Thunderbird users. Evidence limits suggest that additional verification may be required to confirm affected deployments.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-16408 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-16408

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

  • CVE-2026-16408 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-16408

    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.