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CVE-2026-16395 Mozilla CVE debrief

A critical integer overflow vulnerability, CVE-2026-16395, was found in the Audio/Video component of Firefox and Thunderbird. This issue was patched in Firefox 153 and Thunderbird 153. The vulnerability has a CVSS score of 9.8, indicating critical severity. Users should update their browsers to prevent exploitation. The CVE record and NVD entry provide further details on this vulnerability.

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 update their browsers to version 153 to prevent exploitation of this critical vulnerability. This vulnerability affects operators of Firefox and Thunderbird, as well as platform and security teams. The vulnerability has a significant impact on the security posture of affected systems, and defenders should review the CVE record and NVD entry for further details.

Technical summary

CVE-2026-16395 is an integer overflow vulnerability in the Audio/Video component of Firefox and Thunderbird. The vulnerability was patched in Firefox 153 and Thunderbird 153. The CVSS score for this vulnerability is 9.8, indicating a critical severity. This vulnerability affects users of Firefox and Thunderbird, and they should update their browsers to version 153 to prevent exploitation. The technical impact of this vulnerability is significant, and defenders should review the official advisory and CVE record for further details.

Defensive priority

High

Recommended defensive actions

  • Update Firefox to version 153 or later
  • Update Thunderbird to version 153 or later
  • Ensure that all users of Firefox and Thunderbird are aware of the need to update their browsers
  • 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 2026-07-21T13:17:14.733Z and modified on 2026-07-22T20:16:57.870Z. The NVD entry is currently Modified. This information is based on the NVD entry and the CVE record. The vulnerability affects Firefox and Thunderbird, with a CVSS score of 9.8, indicating critical severity. Evidence limits suggest that further verification is required to confirm affected scope and severity.

Official resources

AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-21T13:17:14.733Z and has not been modified since then. The NVD entry is currently Modified.