TI-2026-80424 Aliases CVE-2026-93847 GHSA-8jc7-6qx5-pfvj

Improper post type validation in Mattermost scheduled posts

LOW 16CWE-863Published 2026-10-26 · Updated 2026-11-02

Key facts

Attack vector: Network
Privileges required: Low
User interaction: Required
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. Impact type from CWE-863.

Summary

Mattermost versions 11.7.0 through 11.7.10 fail to validate reserved system post types on the scheduled post creation and publication paths. An authenticated channel member can publish messages that render as trusted system events through the scheduled post endpoint. The flaw is classified as incorrect authorization (CWE-863), and the attacker needs low privileges and user interaction.

Written with Claude Haiku 5.5 from the sources below · 2026-11-02

Description from the CNA

Mattermost versions 11.7.x <= 11.7.10 fail to validate reserved system post types on the scheduled post creation and publication paths which allows an authenticated channel member to publish messages rendering as trusted system events via the scheduled post endpoint.. Mattermost Advisory ID: MMSA-2026-00732

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00174 6th percentileScored 2026-11-07

Fix Fixed Mattermost (Mattermost): 11.11.0, 11.7.11

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	11.7.0 – 11.7.10	11.11.0, 11.7.11	Patch available	CNA

Mattermost VendorMattermost Affected 11.7.0 – 11.7.10 Fixed in 11.11.0, 11.7.11 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:mattermost:mattermost_server::::::::	11.7.0 to before 11.7.11	Vulnerable	Mattermost

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 11.7.0 to before 11.7.11 Vulnerable ·Mattermost

Remediation

Mattermost fixed this in versions 11.7.11 and 11.11.0. Upgrade Mattermost to 11.7.11 or 11.11.0 or later. See Mattermost advisory MMSA-2026-00732.

Written with Claude Haiku 5.5 from the sources below · 2026-11-02

Fix · CNA Mattermost (Mattermost) Fixed in 11.11.0, 11.7.11

Timeline

2026-10-26 Threatist record created from CVE-2026-93847
2026-10-27 Alias added: GHSA-8jc7-6qx5-pfvj
2026-11-02 CISA SSVC decision points changed

References

Advisory 1

MMSA-2026-00732

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

See all 505 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences