CVE-2026-3109: Missing timestamp validation in Zoom webhook handler

Severity: low (CVSS 2.2 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-26 · updated 2026-06-17
Weakness: CWE-754

Description

Mattermost Plugins versions <=11.4 10.11.11.0 fail to validate webhook request timestamps which allows an attacker to corrupt Zoom meeting state in Mattermost via replayed webhook requests. Mattermost Advisory ID: MMSA-2026-00584

Affected products

Mattermost: from 10.11.0 before 10.11.12 — fixed in 10.11.12

How to fix

Upgrade to a fixed version: Mattermost 10.11.12. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

Get alerted when CVE-2026-3109 or the next vulnerability affects your stack