CVE-2026-3590

Description

Mattermost has session spoofing due to lack of single-use consumption of guest magic link tokens enforcement in github.com/mattermost/mattermost-server

How to fix CVE-2026-3590

To remediate CVE-2026-3590, upgrade the affected package to a fixed version below.

• —upgrade to 10.11.13 or later
• —upgrade to 10.11.13+incompatible or later
• —no fix listed
• —no fix listed
• —upgrade to 8.0.0-20250723052842-4cb8d8940332 or later
• —upgrade to 8.0.0-20250723052842-4cb8d8940332 or later

Is CVE-2026-3590 being exploited?

Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.

Affected packages (6)

• >= 10.11.0-rc1, < 10.11.13
• >= 10.11.0-rc1+incompatible, < 10.11.13+incompatible, >= 11.3.0-rc1+incompatible, < 11.3.3+incompatible, >= 11.4.0-rc1+incompatible, < 11.4.3+incompatible, >= 11.5.0-rc1+incompatible, < 11.5.0+incompatible
• from 0
• from 0
• >= 8.0.0-20250721062209-4952acea88ce, < 8.0.0-20250723052842-4cb8d8940332
• >= 8.0.0-20250721062209-4952acea88ce, < 8.0.0-20250723052842-4cb8d8940332

CVSS scores

References (4)

• ADVISORYgithub.com/advisories/GHSA-mh4x-rmrx-3hp4
• ADVISORYnvd.nist.gov/vuln/detail/CVE-2026-3590
• PATCHgithub.com/mattermost/mattermost
• WEBmattermost.com/security-updates