Denial of Service Vulnerability in Mattermost Software by Mattermost
CVE-2026-4915

6.5MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
25 May 2026

What is CVE-2026-4915?

Mattermost versions up to 11.6.0, 11.5.3, 11.4.4, and 10.11.14 have a security issue where nil elements in outgoing webhook attachment payloads are not filtered correctly. This oversight allows authenticated users to exploit crafted webhook callback responses containing null entries, potentially leading to a denial of service by causing the server process to terminate unexpectedly.

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:
6.5
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

daw10
.