CVE-2026-91181

Data Retention Teams Endpoint Leaks Private Team Invite ID

MEDIUM

6.5

CVSS Score

Published: September 14, 2026 at 09:21 PM UTC

Updated: October 7, 2026 at 04:49 PM UTC

2 products affected across 1 vendorMattermost ServerMattermost

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Severity

MEDIUM6.5

Exploit prediction

EPSS 0.4%

SSVC

No known exploit

Description

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

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Mattermost Server · Mattermost

95%

10.11.0 ≤ v < 10.11.2311.7.0 ≤ v < 11.7.811.8.0 ≤ v < 11.8.511.9.0 ≤ v < 11.9.1

Affected range stops below 10.11.23, so it looks safe — our inference, not a vendor statement

Affected range stops below 11.7.8, so it looks safe — our inference, not a vendor statement

Affected range stops below 11.8.5, so it looks safe — our inference, not a vendor statement

Affected range stops below 11.9.1, so it looks safe — our inference, not a vendor statement

Mattermost · Mattermost

60%

10.11.0 ≤ v ≤ 10.11.2211.7.0 ≤ v ≤ 11.7.711.8.0 ≤ v ≤ 11.8.410.11.0 11.7.0 11.8.0 11.9.0

Vendor states this is fixed in 10.11.23 (unaffected)

Vendor states this is fixed in 11.10.0 (unaffected)

Vendor states this is fixed in 11.7.8 (unaffected)

Vendor states this is fixed in 11.8.5 (unaffected)

Vendor states this is fixed in 11.9.1 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://mattermost.com/security-updates

References (1)

Vendor Advisory

Source: cverecord

https://mattermost.com/security-updates

SSVC — Action Prioritization

SSVCNo known exploitNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.5MEDIUMMattermost

Attack Vector: NETWORK
Complexity: LOW
Privileges: HIGH
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: HIGH
Integrity: HIGH
Availability: NONE

Vector?

Quick Info

StatusANALYZED

CWE

CWE-863

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