CVE-2026-20796 json
Time-of-check time-of-use vulnerability in common teams API
published 2026-02-13 8 mo ago modified 2026-06-17 4 mo ago also GHSA-2xf7-hmf6-p64j , GO-2026-4495 , EUVD-2026-7378
- cvss
- 3.1
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 12%
- public exploits
- 0
- none known
Summary
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
Patch / fix
- go github.com/mattermost/mattermost-server 10.11.10, 10.11.10+incompatible
- Mattermost Mattermost 10.11.10, 11.3.0
- govulncheck-vulndb openSUSE Leap 15.6 0.0.20260226T182644-150000.1.149.1
suse advisories SUSE-SU-2026:0757-1
- govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
opensuse advisories openSUSE-SU-2026:21483-1
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 8 mo ago
Exploit prediction
0.22% chance of exploitation in the next 30 days, higher than 12% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 3.1 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N |
| GitHub | 3.1 | 3.1 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/mattermost/mattermost-server | >=10.11.0, <10.11.10 >=10.11.0+incompatible, <10.11.10+incompatible |
10.11.10 10.11.10+incompatible |
Affected products
- Mattermost Mattermost
Classification
- Weakness
-
- CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition
References
-
mattermost.com
/security-updates
vendor-advisory, web
-
nvd.nist.gov
/vuln/detail/CVE-2026-20796
advisory
-
github.com
/mattermost/mattermost
package
-
github.com
/advisories/GHSA-2xf7-hmf6-p64j
advisory
Sources
- CVE List CVE-2026-20796
- GitHub Advisory GHSA-2xf7-hmf6-p64j
- NVD CVE-2026-20796
- OSV GO-2026-4495
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