CVE-2026-20796Network attack vector

Team-name disclosure via stale membership check

Published Feb 13, 2026 · Updated Feb 13, 2026

Information disclosure in Mattermost 10.11.0 through 10.11.9 allows remote authenticated users to learn inaccessible team names. The /common_teams endpoint checks channel membership before retrieving team data and does not revalidate it when an account is deactivated between those operations. Exploitation requires a valid session and a deactivation race; the disclosed impact is limited to team names, not message content or changes.

CVSS severity3.1
Low
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in Mattermost 10.11.0 through 10.11.9 allows remote authenticated users to learn inaccessible team names. The /common_teams endpoint checks channel membership before retrieving team data and does not revalidate it when an account is deactivated between those operations. Exploitation requires a valid session and a deactivation race; the disclosed impact is limited to team names, not message content or changes.

The record

CVE
CVE-2026-20796
Published
Feb 13, 2026
Updated
Feb 13, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-367, CAPEC-29, T1213.005
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 13, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.11.0 <=10.11.9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=10.11.0 <=10.11.9

Published CVSS scores

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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
CAPEC-29Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions
T1213.005Data from Information Repositories: Messaging Applications

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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