Is CVE-2026-5139 actively exploited?

No active exploitation of CVE-2026-5139 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-5139 be exploited remotely?

Yes. CVE-2026-5139 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-5139?

CVE-2026-5139 has a CVSS score of 5.4 (MEDIUM).

HOME VULNERABILITIESCVE-2026-5139

MEDIUM

CVE-2026-5139

CWE-862Published: June 22, 2026· Updated: Jun 23, 2026

5.4

CVSS v3.1

EPSS:0.17%probability of exploitation in 30 daysPercentile:6.5th

Official Description

Mattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 fail to enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler, which allows any authenticated user to overwrite the global default GitLab instance configuration via the {{/gitlab connect <instance-name>}} slash command.. Mattermost Advisory ID: MMSA-2026-00644

NVD Source

Technical Analysis

CVE-2026-5139 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.