EUVD-2026-78160
GHSA-w86c-vmwh-pppx
Severity by source
AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N
Network-reachable API, no complexity, but requires explicit Data Retention Policy role (PR:H); exposes secret tokens and enables unauthorized team join (C:H/I:H); no availability impact.
Primary rating from Vendor (mattermost).
CVSS VectorVendor: mattermost
Lifecycle Timeline
2DescriptionCVE.org
Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 Fail to sanitize Team objects returned by the data retention teams endpoint which allows an authenticated user holding only the read-only Data Retention Policy permission to obtain a private team's secret invite_id and email, and use it to join the team without authorization, via GET /api/v4/data_retention/policies/{policy_id}/teams.. Mattermost Advisory ID: MMSA-2026-00702
AnalysisAI
Mattermost's data retention teams API endpoint fails to sanitize returned Team objects, exposing private teams' secret invite_id and email fields to any authenticated user holding only the read-only Data Retention Policy permission. An attacker exploiting CVE-2026-91181 can call GET /api/v4/data_retention/policies/{policy_id}/teams, harvest the invite_id of private teams they have no membership in, and use it to join those teams without authorization - effectively achieving lateral movement across private channels and communications. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires: (1) Mattermost Enterprise with the Data Retention Policy feature enabled and at least one policy configured; (2) an authenticated user account that has been granted the read-only Data Retention Policy system role - this is NOT a default role and must be explicitly assigned by a system admin; (3) at least one private team associated with a data retention policy. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The vendor-assigned CVSS 6.5 (AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N) accurately reflects the network-reachable API, low complexity once the role is held, and significant confidentiality and integrity impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade to the first version beyond the stated affected ceiling in your release train: beyond 10.11.22 on the 10.11.x branch, beyond 11.7.7 on the 11.7.x branch, beyond 11.8.4 on the 11.8.x branch, or beyond 11.9.0 on the 11.9.x branch. … Detailed patch versions, workarounds, and compensating controls in full report. |
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External POC / Exploit Code
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