CVE-2026-9693

Mattermost versions 10.11.x <= 10.11.20, 11.7.x <= 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allows a previously removed user who is later re-invited to the team to view private channel thread root post content and metadata via the team threads API.. Mattermost Advisory ID: MMSA-2026-00682

CVSS v3 3.5 LOW

3.5^/10

CVSS v3 : LOW

Vector :

Exploitability : 2.1 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction REQUIRED

Confidentiality Impact LOW

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://mattermost.com/security-updates	Vendor Advisory

Configurations

Configuration 1 (hide)

OR	cpe:2.3:a:mattermost:mattermost_server::::::::
	cpe:2.3:a:mattermost:mattermost_server::::::::

History

No history.

Information

Published : 2026-08-17 23:16

Updated : 2026-08-19 13:14

NVD link : CVE-2026-9693

Mitre link : CVE-2026-9693

CVE.ORG link : CVE-2026-9693

JSON object : View

Products Affected

mattermost

mattermost_server

CWE

CWE-459

Incomplete Cleanup

{"id": "CVE-2026-9693", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-9693", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "version": "2.0.3", "timestamp": "2026-08-18T14:20:52.913739Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "responsibledisclosure@mattermost.com", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 3.5, "attackVector": "NETWORK", "baseSeverity": "LOW", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N", "integrityImpact": "NONE", "userInteraction": "REQUIRED", "attackComplexity": "LOW", "availabilityImpact": "NONE", "privilegesRequired": "LOW", "confidentialityImpact": "LOW"}, "impactScore": 1.4, "exploitabilityScore": 2.1}]}, "affected": [{"source": "responsibledisclosure@mattermost.com", "affectedData": [{"vendor": "Mattermost", "product": "Mattermost", "versions": [{"status": "affected", "version": "10.11.0", "versionType": "semver", "lessThanOrEqual": "10.11.20"}, {"status": "affected", "version": "11.7.0", "versionType": "semver", "lessThanOrEqual": "11.7.5"}, {"status": "unaffected", "version": "11.9.0"}, {"status": "unaffected", "version": "10.11.21"}, {"status": "unaffected", "version": "11.7.6"}], "defaultStatus": "unaffected"}]}], "published": "2026-08-17T23:16:52.940", "references": [{"url": "https://mattermost.com/security-updates", "tags": ["Vendor Advisory"], "source": "responsibledisclosure@mattermost.com"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "responsibledisclosure@mattermost.com", "description": [{"lang": "en", "value": "CWE-459"}]}], "descriptions": [{"lang": "en", "value": "Mattermost versions 10.11.x <= 10.11.20, 11.7.x <= 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allows a previously removed user who is later re-invited to the team to view private channel thread root post content and metadata via the team threads API.. Mattermost Advisory ID: MMSA-2026-00682"}], "lastModified": "2026-08-19T13:14:34.433", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "E077E0D9-468B-463D-B269-9445B309D2D5", "versionEndExcluding": "10.11.21", "versionStartIncluding": "10.11.0"}, {"criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "3296B157-E994-4E37-ADB9-355DC1FCFE5B", "versionEndExcluding": "11.7.6", "versionStartIncluding": "11.7.0"}], "operator": "OR"}]}], "sourceIdentifier": "responsibledisclosure@mattermost.com"}