What’s Vulnerable › Vulnerabilities

CVE-2017-18877

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% 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-79

Description

An issue was discovered in Mattermost Server before 4.3.0, 4.2.1, and 4.1.2. XSS attacks could occur against an OAuth 2.0 allow/deny page.

Affected products

• Mattermost: from 4.1.0 before 4.1.2; from 4.2.0 before 4.2.1; 4.3.0-rc1, 4.3.0-rc2, 4.3.0-rc3, 4.3.0-rc4 — fixed in 4.1.2, 4.2.1

How to fix

Upgrade to a fixed version: Mattermost 4.1.2, 4.2.1. Check the vendor advisory for mitigations.

References

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

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