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Fencer Intel
medium 4.5

CVE-2026-19600 json

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

published 24d ago modified 13d ago also EUVD-2026-102744

cvss
4.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 14%
public exploits
0
none known

Summary

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

Patch / fix

  • Mattermost Mattermost 11.7.11, 11.8.6, 11.9.2, 11.10.2, 11.11.0

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
24d ago

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 4.5 CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:N/A:N
NVD 3.1 4.9 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N

Affected products

  • Mattermost Mattermost

Classification

Weakness
  • CWE-532 Insertion of Sensitive Information into Log File

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.