API Misconfiguration in Mattermost Affects User Permissions and Privacy
CVE-2026-18560

4.3MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
16 October 2026

What is CVE-2026-18560?

Certain versions of Mattermost fail to properly validate user permissions before executing other validation checks. This oversight allows unauthorized users to infer the flagged status of posts through direct API calls, potentially exposing sensitive information and compromising user privacy. Users of affected versions should apply patches and updates to mitigate associated risks.

Affected Version(s)

Mattermost 11.10.0

Mattermost 11.7.0 <= 11.7.9

Mattermost 11.9.0 <= 11.9.1

References

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

CVSS V3.1

Score:
4.3
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
None
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

adamsec-dev
.