CVE-2026-19600 Mattermost logs plaintext authentication tokens in debug-level server logs on failed auth attempts
Attackers with log access can steal plaintext authentication tokens from debug logs to impersonate users, requiring log access and debug mode enabled.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-19600?
CVE-2026-19600 is a medium-severity vulnerability in Mattermost Mattermost Server, published on 16 Oct 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
Official description
Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to sanitize authentication tokens before writing them to server log entries, which allows an attacker with access to server logs to obtain valid session tokens or OAuth access tokens and impersonate authenticated users via the debug-level Mattermost server log.. Mattermost Advisory ID: MMSA-2026-00763
Weakness: CWE-532
Which versions are affected by CVE-2026-19600?
It affects 1 product.
Products include Mattermost Mattermost Server.
How do I fix CVE-2026-19600?
No fix has been published for CVE-2026-19600 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-19600 being exploited?
There is no known exploitation of CVE-2026-19600 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-pqq2-2w3v-m8j5.