Channel Access Control Issue in Mattermost by Mattermost
CVE-2026-10085

5.4MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
13 July 2026

What is CVE-2026-10085?

Mattermost versions 11.7.x through 11.7.2, 11.6.x through 11.6.4, and 10.11.x through 10.11.19 possess an access control flaw in the channel patch API. This issue allows group or direct message members to manipulate group participation, specifically by removing all members from a conversation. The flaw arises because the group_constrained channel flag is improperly set, enabling unauthorized actions within channels that should restrict access based on group synchronization.

Affected Version(s)

Mattermost 11.7.0 <= 11.7.2

Mattermost 11.6.0 <= 11.6.4

Mattermost 10.11.0 <= 10.11.19

References

https://mattermost.com/security-updates
vendor-advisory

CVSS V3.1

Score:
5.4
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

se1en
.