GitHub Advisoryadvisory · Go

GHSA-5gmf-x7hg-97wf Mattermost doesn't filter nil elements from outgoing webhook attachment payloads before processing

MEDIUM Published 2026-05-26 Modified 2026-06-30 Official page ↗
Aliases
CVE-2026-4915
Ecosystem
Go
Packages
github.com/mattermost/mattermost-server, github.com/mattermost/mattermost/server/v8
Severity
Moderate
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weaknesses
CWE-754
Reviewed
2026-06-30

Affected packages

• Go github.com/mattermost/mattermost-server: >= 11.6.0, < 11.6.1 → fixed in 11.6.1 • Go github.com/mattermost/mattermost-server: >= 11.5.0, < 11.5.4 → fixed in 11.5.4 • Go github.com/mattermost/mattermost-server: >= 11.4.0, < 11.4.5 → fixed in 11.4.5 • Go github.com/mattermost/mattermost-server: >= 10.11.0, < 10.11.15 → fixed in 10.11.15 • Go github.com/mattermost/mattermost/server/v8: < 8.0.0-20260407102538-faa7d75b4ea0 → fixed in 8.0.0-20260407102538-faa7d75b4ea0

Description

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service (server process termination) via a crafted webhook callback response containing a null attachment entry. Mattermost Advisory ID: MMSA-2026-00641

Related

Alias · CVE (1)

  • CVE-2026-4915 Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to filter nil elements from outgoing… vulnerability

Weakness · CWE (1)

  • CWE-754 Improper Check for Unusual or Exceptional Conditions weakness

References