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Fencer Intel
medium 4.3

CVE-2026-3637 json

Mattermost fails to enforce create_post permission when editing posts

published 5mo ago modified 26d ago also GHSA-v549-xx3c-6pc8 , GO-2026-5651 , EUVD-2026-30741

cvss
4.3
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 4%
public exploits
0
none known

Summary

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

Patch / fix

  • go github.com/mattermost/mattermost/server/v8 8.0.0-20260316171743-090408f09f53, 10.11.14, 11.4.4, 11.5.2
  • go github.com/mattermost/mattermost-server 5.3.2-0.20260316171743-090408f09f53, 10.11.14+incompatible, 11.4.4+incompatible, 11.5.2+incompatible
  • Mattermost Mattermost 10.11.14, 11.4.4, 11.5.2, 11.6.0
  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
5mo ago

Exploit prediction

0.15% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
GitHub 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
go github.com/mattermost/mattermost/server/v8
>=10.11.0, <10.11.14
>=11.4.0, <11.4.4
<8.0.0-20260316171743-090408f09f53
>=11.5.0, <11.5.2
10.11.14
11.4.4
8.0.0-20260316171743-090408f09f53
11.5.2
go github.com/mattermost/mattermost-server
<5.3.2-0.20260316171743-090408f09f53
>=10.11.0+incompatible, <10.11.14+incompatible
>=11.4.0+incompatible, <11.4.4+incompatible
>=11.5.0+incompatible, <11.5.2+incompatible
5.3.2-0.20260316171743-090408f09f53
10.11.14+incompatible
11.4.4+incompatible
11.5.2+incompatible
go github.com/mattermost/mattermost-server/v5
all versions
 no fix listed
go github.com/mattermost/mattermost-server/v6
all versions
 no fix listed

Affected products

  • Mattermost Mattermost

Classification

Weakness

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.