Vulnerability · Published Oct 16, 2026 · Assigned by Mattermost

CVE-2026-19600Mattermost logs plaintext authentication tokens in debug-level server logs on failed auth attempts

Medium 4.5

In plain English

A medium-severity sensitive data in logs in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 15% of all known vulnerabilities).

Severity (CVSS 3.1)4.5Medium

Exploit odds (30 days)0.2%top 85.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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

Affected products (as reported)

Vendor	Product	Versions
Mattermost	Mattermost	11.9.0 – through 11.9.111.8.0 – through 11.8.511.7.0 – through 11.7.1011.10.0 – through 11.10.1

Weakness: CWE-532 · Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:N/A:N

References

MMSA-2026-00763 vendor-advisory