EUVD-2026-38246
GHSA-2g8v-grq3-hq2g
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
Network-reachable slash command with no special configuration needed, but requires an authenticated session (PR:L); global config overwrite yields low integrity and availability impact with no confidentiality exposure.
Primary rating from Vendor (Mattermost).
CVSS VectorVendor: Mattermost
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
Lifecycle Timeline
1DescriptionCVE.org
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
AnalysisAI
The /gitlab connect slash command in Mattermost fails to enforce administrator-level authorization on the setDefaultInstance call, enabling any authenticated user to overwrite the workspace-wide default GitLab instance configuration. Affected across four concurrent release trains (11.7.0, 11.6.x ≤ 11.6.2, 11.5.x ≤ 11.5.5, 10.11.x ≤ 10.11.17), this missing authorization flaw (CWE-862) is exploitable by any valid Mattermost account holder without elevated privileges. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires a valid Mattermost user account - any authenticated session suffices, with no admin role or special channel permission needed (PR:L per CVSS). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The vendor-supplied CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L) scoring 5.4 Medium is consistent with the described behavior. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An authenticated Mattermost user with no administrative privileges types /gitlab connect https://attacker.example.com in any channel where the GitLab plugin is active. The setDefaultInstance function executes without an authorization check, replacing the legitimate global GitLab endpoint with the attacker-controlled URL. … |
| Remediation | Upgrade to a patched Mattermost release per advisory MMSA-2026-00644; consult https://mattermost.com/security-updates for the exact fix version in each affected release train, as precise patched version numbers were not independently confirmed in the available data beyond the advisory reference. … Detailed patch versions, workarounds, and compensating controls in full report. |
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