CVE-2026-5139
Last modified
CVE-2026-5139 is a medium-severity vulnerability rated 5.4/10 on the CVSS scale. 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. EPSS estimates a 0.17% chance of exploitation in the next 30 days.
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
Metrics
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost Server | >= 10.11.0, < 10.11.18 |
| Mattermost | Mattermost Server | >= 11.5.0, < 11.5.6 |
| Mattermost | Mattermost Server | >= 11.6.0, < 11.6.3 |
| Mattermost | Mattermost Server | >= 11.7.0, < 11.7.1 |
References
- https://mattermost.com/security-updatesVendor Advisory
Timeline
- Published
- Last Modified
- Status
- Analyzed
Frequently Asked Questions
What is CVE-2026-5139?
How severe is CVE-2026-5139?
How do I fix CVE-2026-5139?
How Strix Helps
- Uncovering a hidden BOLA in Appsmith's snapshot logicStrix autonomously discovered a BOLA/IDOR vulnerability in Appsmith's snapshot deletion path.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
Related CVEs from 2026
- CVE-2026-5136A flaw was found in Foreman. The Usergroup model in Foreman …8.8
- CVE-2026-5137The RTMKit (rometheme-for-elementor) plugin for WordPress is…4.3
- CVE-2026-5138A flaw was found in Foreman. An authenticated user with host…4.3
- CVE-2026-51380Buffer Overflow vulnerability in Tenda AC10 v3 (firmware V03…9.8
- CVE-2026-51385An issue in safishamsi Open-Source GRAPHIFY v.0.3.2 through …6.9
- CVE-2026-51386Rejected reason: DO NOT USE THIS CVE RECORD. ConsultIDs: CVE…
- CVE-2026-5140Improper neutralization of CRLF sequences ('CRLF injection')…8.8
- CVE-2026-51400An issue in Vim Project v9.2.0389 and earlier allows a local…8.4
- CVE-2026-51401An issue in Vim Project v9.2.0389 and earlier allows a local…7.7
- CVE-2026-5141Improper Privilege Management, Improper Access Control, Inco…8.8
- CVE-2026-5142A flaw was found in foreman. Authenticated users with 'view_…6.5
- CVE-2026-5144The BuddyPress Groupblog plugin for WordPress is vulnerable …8.8
Are you affected by CVE-2026-5139?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST