CVE-2026-19603 json
Private channel ID disclosure via user status endpoints
published 2026-10-16 24 d ago modified 2026-10-29 10 d ago also EUVD-2026-102742
- cvss
- 4.3
- 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 7%
- public exploits
- 0
- none known
Summary
Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to sanitize the active channel field returned by the user status API endpoints, which allows an authenticated user to learn the channel ID of a private channel another user is actively viewing via the status endpoints, without being a member of that channel. Mattermost Advisory ID: MMSA-2026-00765
Patch / fix
- Mattermost Mattermost 11.7.11, 11.8.6, 11.9.2, 11.10.2, 11.11.0
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 24 d ago
Exploit prediction
0.18% chance of exploitation in the next 30 days, higher than 7% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 4.3 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N |
Affected products
- Mattermost Mattermost
Classification
- Weakness
-
- CWE-201 Insertion of Sensitive Information Into Sent Data
References
-
mattermost.com
/security-updates
vendor-advisory
Sources
- CVE List CVE-2026-19603
- NVD CVE-2026-19603
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