CVE-2021-37843: Atlassian SAML Single Sign On

Critical severity, CVSS 9.8. EPSS: 1.5% chance of exploitation in the next 30 days.

The resolution SAML SSO apps for Atlassian products allow a remote attacker to login to a user account when only the username is known (i.e., no other authentication is provided). The fixed versions are for Jira: 3.6.6.1, 4.0.12, 5.0.5; for Confluence 3.6.6, 4.0.12, 5.0.5; for Bitbucket 2.5.9, 3.6.6, 4.0.12, 5.0.5; for Bamboo 2.5.9, 3.6.6, 4.0.12, 5.0.5; and for Fisheye 2.5.9.

Affected products

• Atlassian SAML Single Sign On: before 2.5.9 (fixed in 2.5.9); before 3.5.6 (fixed in 3.5.6); before 3.6.6.1 (fixed in 3.6.6.1); from 3.0.0, before 3.6.6 (fixed in 3.6.6); from 3.6.0, before 3.6.6.1 (fixed in 3.6.6.1); from 4.0.0, before 4.0.12 (fixed in 4.0.12); …

Published 2021-08-02. Last modified 2026-06-17.