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Vulnerability · Published May 18, 2026 · Assigned by Mattermost

CVE-2026-3637Mattermost fails to enforce create_post permission when editing posts

Medium 4.3

In plain English

A medium-severity missing authorization 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 4% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)4.3Medium
Exploit odds (30 days)0.2%top 95.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to check the create_post channel permission during post edit operations which allows an authenticated attacker with revoked posting privileges to modify their existing posts via direct API requests to the post update and patch endpoints.. Mattermost Advisory ID: MMSA-2026-00627

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Gogithub.com/mattermost/mattermost-server10.11.14+incompatible, 11.4.4+incompatible, 11.5.2+incompatibleGO-2026-5651
Gogithub.com/mattermost/mattermost-server5.3.2-0.20260316171743-090408f09f53GHSA-v549-xx3c-6pc8
Gogithub.com/mattermost/mattermost-server/v5no fix listedGO-2026-5651
Gogithub.com/mattermost/mattermost-server/v6no fix listedGO-2026-5651
Gogithub.com/mattermost/mattermost/server/v810.11.14GHSA-v549-xx3c-6pc8
Gogithub.com/mattermost/mattermost/server/v88.0.0-20260316171743-090408f09f53GO-2026-5651
Gogithub.com/mattermost/mattermost/server/v811.4.4GHSA-v549-xx3c-6pc8
Gogithub.com/mattermost/mattermost/server/v88.0.0-20260316171743-090408f09f53GHSA-v549-xx3c-6pc8
Gogithub.com/mattermost/mattermost/server/v811.5.2GHSA-v549-xx3c-6pc8

Affected products (as reported)

VendorProductVersions
Mattermost Mattermost 11.5.0 – through 11.5.110.11.0 – through 10.11.1311.4.0 – through 11.4.3

Weakness: CWE-862 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

References