UpHeron
All vulnerabilities

Servers and applications

CVE-2026-18551

Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to validate the combination of guest and admin scheme roles which allows an authenticated attacker to escalate a guest account to team or channel admin via a crafted PUT request to the member roles API endpoint.. Mattermost Advisory ID: MMSA-2026-00752

Severity
Medium 6.5
Published
16 Oct 2026
Last changed
29 Oct 2026
Added to UpHeron
1 Nov 2026
Fixed in
11.7.10, 11.8.6, 11.9.2
Sources
NVD

Affected software

SoftwareAffected versions
MattermostServers and applications · cpe:a:mattermost:mattermost_server
  • From 11.7.0 before 11.7.10
  • From 11.8.0 before 11.8.6
  • From 11.9.0 before 11.9.2
  • Version 11.10.0

References

  • NVD https://nvd.nist.gov/vuln/detail/CVE-2026-18551
  • CVE.org https://www.cve.org/CVERecord?id=CVE-2026-18551