CVE-2026-20796
Race Condition in Mattermost 10.11.x Allows Unauthorized Data Access
Publication date: 2026-02-13
Last updated on: 2026-02-23
Assigner: Mattermost, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| mattermost | mattermost_server | From 10.11.0 (inc) to 10.11.10 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-367 | The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability affects Mattermost versions 10.11.x up to and including 10.11.9. It occurs because the software fails to properly validate whether a user is a member of a channel when retrieving data. Specifically, a deactivated user can exploit a race condition in the /common_teams API endpoint to learn the names of teams they should not have access to.
How can this vulnerability impact me? :
The impact of this vulnerability is that a deactivated user may be able to discover team names that they are not authorized to see. Although the vulnerability has a low CVSS base score of 3.1, indicating limited severity, it can lead to unauthorized disclosure of some information about team memberships.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
I don't know