Post Ownership Verification Vulnerability in Mattermost by Mattermost
CVE-2026-10103

4.3MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
13 July 2026

What is CVE-2026-10103?

Mattermost suffers from a vulnerability where insufficient verification of post ownership occurs in the shared channel inbound sync handler. This flaw allows an authenticated remote cluster to manipulate posts created by local users or other remote users. By sending malicious sync messages with arbitrary post IDs, an attacker can delete or alter existing posts, compromising the integrity of the shared channel.

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:
4.3
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

ratrarity
.