Users can view the contents of an archived channel when access is explicitly denied by the system admin
Priority LOW 30CWE-284Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- High · None · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-284.
Summary
Mattermost 6.1 and earlier fails to sufficiently validate permissions while viewing archived channels, which allows authenticated users to view contents of archived channels even when this is denied by system administrators by directly accessing the APIs.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00585 48th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 6.2
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Mattermost | Mattermost | before 6.2 | 6.2 | Patch available | CNA |
- Mattermost VendorMattermost Affected before 6.2 Fixed in 6.2 Patch available CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mattermost:mattermost:*:*:*:*:*:*:*:* | up to 6.1 | Vulnerable | Mattermost |
- cpe:2.3:a:mattermost:mattermost:*:*:*:*:*:*:*:* Versions up to 6.1 Vulnerable ·Mattermost
Remediation
- Fix · CNA Mattermost (Mattermost) Fixed in 6.2
Timeline
- 2026-10-02 Threatist record created from CVE-2021-37864
- 2026-10-03 Alias added: GHSA-898c-6fq9-5cv9
References
Advisory 1
More Mattermost vulnerabilities
- TI-2024-26695 Malicious remote can invite itself to an arbitrary local channel CVSS 3.1CRITICAL 9.6
- TI-2023-02056 Oauth authorization codes do not expire when deauthorizing an oauth2 app CVSS 3.1CRITICAL 9.1
- TI-2019-15069 An issue was discovered in Mattermost Mobile Apps before 1.26.0. CVSS 3.1CRITICAL 9.1
- TI-2024-26233 Malicious remote can add users to arbitrary teams and channels CVSS 3.1HIGH 8.7
- TI-2024-26746 Permanently local data deletion by malicious remote CVSS 3.1HIGH 8.7
- TI-2023-06508 Injection in Mattermost CVSS 3.1HIGH 8.8
Sources
- CVE-2021-37864 · CVE Program
- CVE-2021-37864 · NVD
- FIRST EPSS
- GHSA-898c-6fq9-5cv9 · GitHub Advisory Database · CC BY 4.0
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