An issue was discovered in Mattermost Server before 5.7.1, 5.6.4, 5.5.3, and 4.10.6.
Priority LOW 21CWE-862Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- Low · None · None
- Fix status
- No fix listed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-862.
Summary
An issue was discovered in Mattermost Server before 5.7.1, 5.6.4, 5.5.3, and 4.10.6. It does not honor flags API permissions when deciding whether a user can receive intra-team posts.
Why it matters now
EPSS 0.00651 51st percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | — | all versions | — | No fix listed | CNA |
- — Vendor— Affected all versions Fixed in — No fix listed CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | before 4.10.6; 5.5.0 to before 5.5.3; 5.6.0 to before 5.6.4; 5.7.0 to before 5.7.1 | Vulnerable | Mattermost |
- cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions before 4.10.6; 5.5.0 to before 5.5.3; 5.6.0 to before 5.6.4; 5.7.0 to before 5.7.1 Vulnerable ·Mattermost
Remediation
No fixed version listed by the sources yet.
Timeline
- 2026-10-02 Threatist record created from CVE-2019-20887
- 2026-10-03 Alias added: GHSA-24mg-7j8x-g2w5
- 2026-10-14 EPSS moved to the 50th–90th percentile
References
Advisory 1
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-2019-20887 · CVE Program
- CVE-2019-20887 · NVD
- FIRST EPSS
- GHSA-24mg-7j8x-g2w5 · 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