CVE-2018-21255
An issue was discovered in Mattermost Server before 5.1. Non-members of a channel could use the...
An issue was discovered in Mattermost Server before 5.1. Non-members of a channel could use the Channel PATCH API to modify that channel.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- 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. Non-members of a channel could use the Channel PATCH API to modify that channel.
- Record
CVE-2018-21255- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N - CVSS 2.0
- 4.0 Medium
AV:N/AC:L/Au:S/C:N/I:P/A:N - Weakness
- CWE-732
- Updated
- 2026-11-02
CVE List No score
An issue was discovered in Mattermost Server before 5.1. Non-members of a channel could use the Channel PATCH API to modify that channel.
- Record
CVE-2018-21255- Updated
- 2026-11-02
EUVDEUVD-2018-13770 No score
An issue was discovered in Mattermost Server before 5.1. Non-members of a channel could use the Channel PATCH API to modify that channel.
- Record
EUVD-2018-13770- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-3j37-f63q-jrwq No score
An issue was discovered in Mattermost Server before 5.1. Non-members of a channel could use the...
An issue was discovered in Mattermost Server before 5.1. Non-members of a channel could use the Channel PATCH API to modify that channel.
- Record
GHSA-3j37-f63q-jrwq- Updated
- 2026-11-02
OSV
An issue was discovered in Mattermost Server before 5.1. Non-members of a channel could use the Channel PATCH API to modify that channel.
- Record
CVE-2018-21255- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/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-2018-21255 is a medium vulnerability (CVSS 4.3) 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 0.58%, the 48th percentile. No source names a fixed version.