What’s Vulnerable › Vulnerabilities

CVE-2018-21255

• Severity: medium (CVSS 4.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-06-19 · updated 2026-06-17
• Weakness: CWE-732

Description

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.

Affected products

• Mattermost: before 5.1.0 — fixed in 5.1.0

How to fix

Upgrade to a fixed version: Mattermost 5.1.0. Check the vendor advisory for mitigations.

References

• https://mattermost.com/security-updates/
• https://mattermost.com/security-updates/

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