Mattermost Server exposes sensitive user credentials during shared channel membership synchronization
Priority LOW 30CWE-862Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- High
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- High · High · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-862.
Summary
Mattermost versions 10.10.x <= 10.10.1 fail to properly sanitize user data during shared channel membership synchronization, which allows malicious or compromised remote clusters to access sensitive user information via unsanitized user objects. This vulnerability affects Mattermost Server instances with shared channels enabled.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0026 17th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 10.11.0, 10.10.2github.com/mattermost/mattermost/server/v8 (Go): 8.0.0-20250729073403-517ae758cd02+1 more product
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Total
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 | 10.10.0 – 10.10.1 | 10.11.0, 10.10.2 | Patch available | CNA |
| — | github.com/mattermost/mattermost/server/v8 (Go) | before 8.0.0-20250729073403-517ae758cd02 | 8.0.0-20250729073403-517ae758cd02 | Patch available | GHSA-3vcm-c42p-3hhf |
| — | github.com/mattermost/mattermost-server (Go) | 10.10.0 to before 10.10.2 | 10.10.2 | Patch available | GHSA-3vcm-c42p-3hhf |
- Mattermost VendorMattermost Affected 10.10.0 – 10.10.1 Fixed in 10.11.0, 10.10.2 Patch available CNA
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected before 8.0.0-20250729073403-517ae758cd02 Fixed in 8.0.0-20250729073403-517ae758cd02 Patch available GHSA-3vcm-c42p-3hhf
- github.com/mattermost/mattermost-server (Go) Vendor— Affected 10.10.0 to before 10.10.2 Fixed in 10.10.2 Patch available GHSA-3vcm-c42p-3hhf
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | 10.10.0 to before 10.10.2 | Vulnerable | Mattermost |
- cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 10.10.0 to before 10.10.2 Vulnerable ·Mattermost
Remediation
- Fix · CNA Mattermost (Mattermost) Fixed in 10.11.0, 10.10.2
- Fix · GHSA-3vcm-c42p-3hhf github.com/mattermost/mattermost/server/v8 (Go) Fixed in 8.0.0-20250729073403-517ae758cd02 Advisory →
- Fix · GHSA-3vcm-c42p-3hhf github.com/mattermost/mattermost-server (Go) Fixed in 10.10.2 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2025-9076
- 2026-10-03 Alias added: GHSA-3vcm-c42p-3hhf
References
More Mattermost Server vulnerabilities
- TI-2025-18933 Arbitrary file read in Mattermost Boards via import & export board archive CVSS 3.1CRITICAL 9.9
- TI-2025-04465 Path Traversal Leading to RCE by Any Authenticated Mattermost User CVSS 3.1CRITICAL 9.9
- TI-2017-14068 An issue was discovered in Mattermost Server before 3.6.2. CVSS 3.1CRITICAL 9.8
- TI-2017-14060 An issue was discovered in Mattermost Server before 3.8.2, 3.7.5, and 3.6.7. CVSS 3.1CRITICAL 9.8
- TI-2017-14048 An issue was discovered in Mattermost Server before 4.1.0, 4.0.4, and 3.10.3. CVSS 3.1CRITICAL 9.8
- TI-2025-14360 Arbitrary file read via block duplication in Mattermost Boards CVSS 3.1CRITICAL 9.9
Sources
- CVE-2025-9076 · CVE Program
- CVE-2025-9076 · NVD
- FIRST EPSS
- GHSA-3vcm-c42p-3hhf · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences