CVE-2026-9693
Mattermost thread memberships persist after team removal, exposing private channel thread metadata on re-invite
Description
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
INFO
Published Date :
Aug. 17, 2026, 11:16 p.m.
Last Modified :
Aug. 19, 2026, 1:14 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-9693
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | LOW | 9302f53e-dde5-4bf3-b2f2-a83f91ac0eee | ||||
| CVSS 3.1 | LOW | [email protected] | ||||
| CVSS 3.1 | LOW | MITRE-CVE |
Solution
- Update Mattermost to a fixed version.
- Verify user access controls.
- Review thread membership data.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-9693.
| URL | Resource |
|---|---|
| https://mattermost.com/security-updates | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-9693 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-9693
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-9693 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-9693 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Aug. 19, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* versions from (including) 10.11.0 up to (excluding) 10.11.21 *cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* versions from (including) 11.7.0 up to (excluding) 11.7.6 Added Reference Type Mattermost, Inc.: https://mattermost.com/security-updates Types: Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 18, 2026
Action Type Old Value New Value Added SSVC {'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'} -
New CVE Received by [email protected]
Aug. 17, 2026
Action Type Old Value New Value Added Affected [{'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'}] Added Description 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 Added CVSS V3.1 AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N Added CWE CWE-459 Added Reference https://mattermost.com/security-updates