Mattermost fails to enforce create_post permission when editing posts
Priority LOW 19CWE-862Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- None · Low · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-862.
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
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00152 4th percentileScored 2026-11-08
Fix Fixed Mattermost (Mattermost): 11.6.0, 11.5.2, 10.11.14 +1github.com/mattermost/mattermost/server/v8 (Go): 10.11.14, 11.4.4, 8.0.0-20260316171743-090408f09f53 +1+1 more product
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Mattermost | Mattermost | 11.5.0 – 11.5.1; 10.11.0 – 10.11.13; 11.4.0 – 11.4.3 | 11.6.0, 11.5.2, 10.11.14, 11.4.4 | Patch available | CNA |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 10.11.0 to before 10.11.14 | 10.11.14 | Patch available | GHSA-v549-xx3c-6pc8 |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 11.4.0 to before 11.4.4 | 11.4.4 | Patch available | GHSA-v549-xx3c-6pc8 |
| — | github.com/mattermost/mattermost/server/v8 (Go) | before 8.0.0-20260316171743-090408f09f53 | 8.0.0-20260316171743-090408f09f53 | Patch available | GHSA-v549-xx3c-6pc8 |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 11.5.0 to before 11.5.2 | 11.5.2 | Patch available | GHSA-v549-xx3c-6pc8 |
| — | github.com/mattermost/mattermost-server (Go) | before 5.3.2-0.20260316171743-090408f09f53 | 5.3.2-0.20260316171743-090408f09f53 | Patch available | GHSA-v549-xx3c-6pc8 |
- Mattermost VendorMattermost Affected 11.5.0 – 11.5.1; 10.11.0 – 10.11.13; 11.4.0 – 11.4.3 Fixed in 11.6.0, 11.5.2, 10.11.14, 11.4.4 Patch available CNA
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 10.11.0 to before 10.11.14 Fixed in 10.11.14 Patch available GHSA-v549-xx3c-6pc8
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 11.4.0 to before 11.4.4 Fixed in 11.4.4 Patch available GHSA-v549-xx3c-6pc8
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected before 8.0.0-20260316171743-090408f09f53 Fixed in 8.0.0-20260316171743-090408f09f53 Patch available GHSA-v549-xx3c-6pc8
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 11.5.0 to before 11.5.2 Fixed in 11.5.2 Patch available GHSA-v549-xx3c-6pc8
- github.com/mattermost/mattermost-server (Go) Vendor— Affected before 5.3.2-0.20260316171743-090408f09f53 Fixed in 5.3.2-0.20260316171743-090408f09f53 Patch available GHSA-v549-xx3c-6pc8
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | 10.11.0 to before 10.11.14; 11.4.0 to before 11.4.4; 11.5.0 to before 11.5.2 | Vulnerable | Mattermost |
- cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 10.11.0 to before 10.11.14; 11.4.0 to before 11.4.4; 11.5.0 to before 11.5.2 Vulnerable ·Mattermost
Remediation
- Fix · CNA Mattermost (Mattermost) Fixed in 11.6.0, 11.5.2, 10.11.14, 11.4.4
- Fix · GHSA-v549-xx3c-6pc8 github.com/mattermost/mattermost/server/v8 (Go) Fixed in 10.11.14 Advisory →
- Fix · GHSA-v549-xx3c-6pc8 github.com/mattermost/mattermost/server/v8 (Go) Fixed in 11.4.4 Advisory →
- Fix · GHSA-v549-xx3c-6pc8 github.com/mattermost/mattermost/server/v8 (Go) Fixed in 8.0.0-20260316171743-090408f09f53 Advisory →
- Fix · GHSA-v549-xx3c-6pc8 github.com/mattermost/mattermost/server/v8 (Go) Fixed in 11.5.2 Advisory →
- Fix · GHSA-v549-xx3c-6pc8 github.com/mattermost/mattermost-server (Go) Fixed in 5.3.2-0.20260316171743-090408f09f53 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-3637
- 2026-10-03 Alias added: GHSA-v549-xx3c-6pc8
References
More Mattermost Server vulnerabilities
- TI-2025-18933 Arbitrary file read in Mattermost Boards via import & export board archive CVSS 3.1CRITICAL 9.9
- TI-2025-04465 Path Traversal Leading to RCE by Any Authenticated Mattermost User CVSS 3.1CRITICAL 9.9
- TI-2017-14068 An issue was discovered in Mattermost Server before 3.6.2. CVSS 3.1CRITICAL 9.8
- TI-2017-14060 An issue was discovered in Mattermost Server before 3.8.2, 3.7.5, and 3.6.7. CVSS 3.1CRITICAL 9.8
- TI-2017-14048 An issue was discovered in Mattermost Server before 4.1.0, 4.0.4, and 3.10.3. CVSS 3.1CRITICAL 9.8
- TI-2025-14360 Arbitrary file read via block duplication in Mattermost Boards CVSS 3.1CRITICAL 9.9
Sources
- CVE-2026-3637 · CVE Program
- CVE-2026-3637 · NVD
- FIRST EPSS
- GHSA-v549-xx3c-6pc8 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences