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VulnerabilityPublished

CVE-2026-19076: Mattermost · Incorrect Authorization

Affects MattermostSource GCVE Database

0

Not known to be exploited · CVSS 4.4 Medium.

Data as of 27 Oct 2026, 22:42 UTC

CVSS 3.1 base score
4.4Medium
How severe the flaw is on the 0–10 CVSS scale.
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 16 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
Mattermost MattermostAffected
  • 11.7.0 – 11.10.0
4 affected builds
Fixed in–

AI-suggested

Until a fix is available, restrict OAuth bearer token distribution and monitor for suspicious activity involving the /api/v4/users/login/switch endpoint.

Description

CVE-2026-19076 is an incorrect authorization vulnerability in Mattermost affecting certain 11.x versions. It allows an attacker with a valid OAuth bearer token for a target user to permanently take over that user's SSO-backed account by exploiting the account type switch endpoint. The attacker can set a password and detach the account from its identity provider via a crafted POST request to /api/v4/users/login/switch. This vulnerability impacts Mattermost versions 11.10.0, 11.7.0, 11.9.0, and 11.8.0.

References

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