API Request Handler Vulnerability in Mattermost Applications
CVE-2026-4646

4.3MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
22 May 2026

What is CVE-2026-4646?

A flaw exists in multiple versions of Mattermost wherein the software fails to properly validate input from users in API request handlers. This vulnerability permits an authenticated attacker to exploit the system through a specially crafted HTTP request targeted at the PR details endpoint, potentially leading to a process crash. Affected versions include several from the 11.6.x, 11.5.x, 11.4.x, and 10.11.x series, necessitating prompt updates to mitigate associated risks.

Affected Version(s)

Mattermost 11.6.0

Mattermost 11.5.0 <= 11.5.3

Mattermost 11.4.0 <= 11.4.4

References

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

CVSS V3.1

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

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Mariusz Maik
.