{"id":"USN-6901-1","summary":"stunnel4 vulnerability","details":"It was discovered that stunnel did not properly validate client\ncertificates when configured to use both the redirect and verifyChain\noptions. A remote attacker could potentially use this issue to obtain\nsensitive information by accessing the tunneled service.\n","modified":"2026-02-10T04:44:41Z","published":"2024-07-18T05:18:18Z","related":["UBUNTU-CVE-2021-20230"],"upstream":["CVE-2021-20230","UBUNTU-CVE-2021-20230"],"references":[{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-6901-1"},{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2021-20230"}],"affected":[{"package":{"name":"stunnel4","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/stunnel4@3:5.44-1ubuntu3+esm1?arch=source&distro=esm-apps/bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3:5.44-1ubuntu3+esm1"}]}],"versions":["3:5.39-2","3:5.42-1","3:5.44-1ubuntu1","3:5.44-1ubuntu2","3:5.44-1ubuntu3"],"ecosystem_specific":{"binaries":[{"binary_name":"stunnel4","binary_version":"3:5.44-1ubuntu3+esm1"}],"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-6901-1.json","cves_map":{"ecosystem":"Ubuntu:Pro:18.04:LTS","cves":[{"severity":[{"score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","type":"CVSS_V3"},{"score":"medium","type":"Ubuntu"}],"id":"CVE-2021-20230"}]}}},{"package":{"name":"stunnel4","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/stunnel4@3:5.56-1ubuntu0.2?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3:5.56-1ubuntu0.2"}]}],"versions":["3:5.55-2build1","3:5.56-1"],"ecosystem_specific":{"binaries":[{"binary_name":"stunnel4","binary_version":"3:5.56-1ubuntu0.2"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-6901-1.json","cves_map":{"ecosystem":"Ubuntu:20.04:LTS","cves":[{"severity":[{"score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","type":"CVSS_V3"},{"score":"medium","type":"Ubuntu"}],"id":"CVE-2021-20230"}]}}}],"schema_version":"1.7.3"}