CVE-2026-3109 Missing timestamp validation in Zoom webhook handler
Attackers can corrupt Zoom meeting state in Mattermost by replaying webhook requests due to missing timestamp validation.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-3109?
CVE-2026-3109 is a low-severity vulnerability in Mattermost Mattermost Server, published on 26 Mar 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Official 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
Weakness: CWE-754
Which versions are affected by CVE-2026-3109?
It affects 1 product.
Products include Mattermost Mattermost Server.
How do I fix CVE-2026-3109?
No fix has been published for CVE-2026-3109 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-3109 being exploited?
There is no known exploitation of CVE-2026-3109 in the wild and no public exploit code.
Other vulnerabilities in Mattermost Mattermost Server
- CVE-2025-12419 Account takeover on OAuth/OpenID-enabled servers
- CVE-2025-12421 Account Takeover via Code Exchange Endpoint
- CVE-2025-4981 Path Traversal Leading to RCE by Any Authenticated Mattermost User
- CVE-2025-20051 Arbitrary file read via block duplication in Mattermost Boards
- CVE-2025-25279 Arbitrary file read in Mattermost Boards via import & export board archive
Sources
Also known as GHSA-pv8w-wmj3-q39p.