CVE-2018-21257
An issue was discovered in Mattermost Server before 5.1. It allows attackers to bypass intended...
An issue was discovered in Mattermost Server before 5.1. It allows attackers to bypass intended access restrictions (for setting a channel header) via the Channel header slash command API.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
An issue was discovered in Mattermost Server before 5.1. It allows attackers to bypass intended access restrictions (for setting a channel header) via the Channel header slash command API.
- Record
CVE-2018-21257- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N - CVSS 2.0
- 5.0 Medium
AV:N/AC:L/Au:N/C:N/I:P/A:N - Weakness
- CWE-862
- Updated
- 2026-11-02
CVE List No score
An issue was discovered in Mattermost Server before 5.1. It allows attackers to bypass intended access restrictions (for setting a channel header) via the Channel header slash command API.
- Record
CVE-2018-21257- Updated
- 2026-11-02
EUVDEUVD-2018-13772 No score
An issue was discovered in Mattermost Server before 5.1. It allows attackers to bypass intended access restrictions (for setting a channel header) via the Channel header slash command API.
- Record
EUVD-2018-13772- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-qg8w-6226-7h2q No score
An issue was discovered in Mattermost Server before 5.1. It allows attackers to bypass intended...
An issue was discovered in Mattermost Server before 5.1. It allows attackers to bypass intended access restrictions (for setting a channel header) via the Channel header slash command API.
- Record
GHSA-qg8w-6226-7h2q- Updated
- 2026-11-02
OSV
An issue was discovered in Mattermost Server before 5.1. It allows attackers to bypass intended access restrictions (for setting a channel header) via the Channel header slash command API.
- Record
CVE-2018-21257- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N - Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2018-21257 is a medium vulnerability (CVSS 5.3) in Mattermost Server, published June 19, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.81%, the 57th percentile. No source names a fixed version.