What’s Vulnerable › Vulnerabilities

CVE-2025-9072: One-Click Mattermost Account Takeover via Poisoned RelayState SAML Parameter

• Severity: medium (CVSS 5.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-09-15 · updated 2026-10-19
• Weakness: CWE-601

Description

Mattermost versions 10.10.x <= 10.10.1, 10.5.x <= 10.5.9, 10.9.x <= 10.9.4 fail to validate the redirect_to parameter, allowing an attacker to craft a malicious link that, once a user authenticates with their SAML provider, could post the user’s cookies to an attacker-controlled URL.

Affected products

• Mattermost: from 10.5.0 before 10.5.10; from 10.9.0 before 10.9.5; from 10.10.0 before 10.10.2 — fixed in 10.10.2, 10.5.10, 10.9.5

How to fix

Upgrade to a fixed version: Mattermost 10.10.2, 10.5.10, 10.9.5. Check the vendor advisory for mitigations.

References

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

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