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TI-2026-82236 Aliases CVE-2026-93851GHSA-jq9q-vph7-fh8w

Path traversal in Mattermost Agents plugin allows plugin replacement

Priority LOW 36CWE-22Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
Required
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

Mattermost versions 11.9.0 through 11.9.1, 11.8.0 through 11.8.5 and 11.7.0 through 11.7.10 fail to validate the target post ID in the Agents plugin's mention reminder component. An authenticated user who can post in a channel visible to a system administrator can send a crafted post containing a forged mention reminder, and when the administrator clicks it, the administrator's browser sends an unintended API request that replaces an installed plugin, leading to code execution on the server. The weakness is classified as CWE-22.

Written with Claude Haiku 5.5 from the sources below · 2026-11-05

Description from the CNA

Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10 fail to validate the target post ID in the Agents plugin's mention reminder component, which allows an authenticated user who can post in a channel visible to a system administrator to cause the administrator's browser to send an unintended API request, resulting in replacement of an installed plugin and code execution on the server, via a crafted post containing a forged mention reminder that the administrator clicks. Mattermost Advisory ID: MMSA-2026-00742

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00266 18th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 11.10.0, 11.9.2, 11.8.6 +1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MattermostMattermost11.9.0 – 11.9.1; 11.8.0 – 11.8.5; 11.7.0 – 11.7.1011.10.0, 11.9.2, 11.8.6, 11.7.11Patch availableCNA
  • Mattermost VendorMattermost Affected 11.9.0 – 11.9.1; 11.8.0 – 11.8.5; 11.7.0 – 11.7.10 Fixed in 11.10.0, 11.9.2, 11.8.6, 11.7.11 Patch available CNA

Remediation

Upgrade Mattermost to 11.10.0, 11.9.2, 11.8.6 or 11.7.11, depending on the release branch in use. The fixes are documented in advisory MMSA-2026-00742.

Written with Claude Haiku 5.5 from the sources below · 2026-11-05

  • Fix · CNA Mattermost (Mattermost) Fixed in 11.10.0, 11.9.2, 11.8.6, 11.7.11

Timeline

  1. 2026-10-28 Threatist record created from CVE-2026-93851
  2. 2026-10-29 Alias added: GHSA-jq9q-vph7-fh8w
  3. 2026-10-29 CISA SSVC decision points changed
  4. 2026-10-29 Priority changed: MEDIUM → LOW
  5. 2026-10-30 CISA SSVC decision points changed

References

Advisory 1

  • TI-2025-18933 Arbitrary file read in Mattermost Boards via import & export board archive CVSS 3.1CRITICAL 9.9
  • TI-2019-15071 An issue was discovered in Mattermost Packages before 5.16.3. CVSS 3.1CRITICAL 9.8
  • TI-2025-04465 Path Traversal Leading to RCE by Any Authenticated Mattermost User CVSS 3.1CRITICAL 9.9
  • TI-2019-15074 An issue was discovered in Mattermost Desktop App before 4.3.0 on macOS. CVSS 3.1CRITICAL 9.8
  • 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
See all 670 →

Sources

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