CVE-2026-20796 | BDVDB-2026-315340 Detail

MattermostMattermost

Description#

Mattermost versions 10.11.x <= 10.11.9 fail to properly validate channel membership at the time of data retrieval which allows a deactivated user to learn team names they should not have access to via a race condition in the /common_teams API endpoint.. Mattermost Advisory ID: MMSA-2025-00549

Impact#

Per CVSS v3.1: confidentiality impact low, integrity impact none, availability impact none. Attack vector: network.

Weaknesses#

CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

References#

https://mattermost.com/security-updates

Exploit#

No public exploit known

History#

Version 12026-02-13Record published in the CVE List.

Published

Published: 2026-02-13
Last modified: 2026-02-13

Vendor information

Vendor: Mattermost
Product: Mattermost

All Mattermost vulnerabilities

Score

3.1 Low

EPSS

less than 1%, Very Low

Estimated chance of exploitation in the next 30 days. EPSS percentile: 12.2.

KEV

Not listed in the CISA Known Exploited Vulnerabilities catalog.

Impact

Race Condition

Action

No specific action is recorded in the source data. Check the references for vendor guidance.

Affected Systems

Vulnerable
>= 10.11.0 and <= 10.11.9
Fixed
Not stated
Vulnerable
Not stated
Fixed
11.3.0
Vulnerable
Not stated
Fixed
10.11.10

Scoring System

CVSS v4.0

Not available

CVSS v3.1

3.1 Low

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N

Metric breakdown
Attack Vector	Network
Attack Complexity	High
Privileges Required	Low
User Interaction	None
Scope	Unchanged
Confidentiality	Low
Integrity	None
Availability	None

CVSS v3.0

Not available

CVSS v2

Not available

Source: CVE List v5 (record); CISA KEV (kev, action); FIRST EPSS (epss).