CVE-2020-26276: Fleetdm Fleet

Critical severity, CVSS 9.8. EPSS: 2.2% chance of exploitation in the next 30 days.

Fleet is an open source osquery manager. In Fleet before version 3.5.1, due to issues in Go's standard library XML parsing, a valid SAML response may be mutated by an attacker to modify the trusted document. This can result in allowing unverified logins from a SAML IdP. Users that configure Fleet with SSO login may be vulnerable to this issue. This issue is patched in 3.5.1. The fix was made using https://github.com/mattermost/xml-roundtrip-validator If upgrade to 3.5.1 is not possible, users should disable SSO authentication in Fleet.

Affected products

• Fleetdm Fleet: before 3.5.1 (fixed in 3.5.1)

Published 2020-12-17. Last modified 2026-06-17.