UpHeron
All vulnerabilities

Servers and applications

CVE-2026-19603

Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to sanitize the active channel field returned by the user status API endpoints, which allows an authenticated user to learn the channel ID of a private channel another user is actively viewing via the status endpoints, without being a member of that channel. Mattermost Advisory ID: MMSA-2026-00765

Severity
Medium 4.3
Published
16 Oct 2026
Last changed
29 Oct 2026
Added to UpHeron
1 Nov 2026
Fixed in
11.7.11, 11.8.6, 11.9.2, 11.10.2
Sources
NVD

Affected software

SoftwareAffected versions
MattermostServers and applications · cpe:a:mattermost:mattermost_server
  • From 11.7.0 before 11.7.11
  • From 11.8.0 before 11.8.6
  • From 11.9.0 before 11.9.2
  • From 11.10.0 before 11.10.2

References

  • NVD https://nvd.nist.gov/vuln/detail/CVE-2026-19603
  • CVE.org https://www.cve.org/CVERecord?id=CVE-2026-19603