{"id":"UBUNTU-CVE-2021-36367","details":"PuTTY through 0.75 proceeds with establishing an SSH session even if it has never sent a substantive authentication response. This makes it easier for an attacker-controlled SSH server to present a later spoofed authentication prompt (that the attacker can use to capture credential data, and use that data for purposes that are undesired by the client user).","modified":"2025-10-24T04:50:26Z","published":"2021-07-09T21:15:00Z","upstream":["CVE-2021-36367"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2021-36367"},{"type":"REPORT","url":"https://git.tartarus.org/?p=simon/putty.git;a=commit;h=1dc5659aa62848f0aeb5de7bd3839fecc7debefa"},{"type":"REPORT","url":"https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2021-36367"}],"affected":[{"package":{"name":"putty","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/putty@0.67-3+deb9u1build0.16.04.1?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.65-2","0.66-1","0.66-2","0.66-3","0.66-4","0.67-1","0.67-2","0.67-3build0.16.04.1","0.67-3+deb9u1build0.16.04.1"],"ecosystem_specific":{"binaries":[{"binary_version":"0.67-3+deb9u1build0.16.04.1","binary_name":"pterm"},{"binary_version":"0.67-3+deb9u1build0.16.04.1","binary_name":"putty"},{"binary_version":"0.67-3+deb9u1build0.16.04.1","binary_name":"putty-tools"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-36367.json"}},{"package":{"name":"putty","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/putty@0.70-4?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.70-1","0.70-2","0.70-3","0.70-4"],"ecosystem_specific":{"binaries":[{"binary_version":"0.70-4","binary_name":"pterm"},{"binary_version":"0.70-4","binary_name":"putty"},{"binary_version":"0.70-4","binary_name":"putty-tools"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-36367.json"}},{"package":{"name":"putty","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/putty@0.73-2?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.72-1","0.73-1","0.73-2"],"ecosystem_specific":{"binaries":[{"binary_version":"0.73-2","binary_name":"pterm"},{"binary_version":"0.73-2","binary_name":"putty"},{"binary_version":"0.73-2","binary_name":"putty-tools"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-36367.json"}},{"package":{"name":"putty","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/putty@0.76-2?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.75-3","0.76-1","0.76-2"],"ecosystem_specific":{"binaries":[{"binary_version":"0.76-2","binary_name":"pterm"},{"binary_version":"0.76-2","binary_name":"putty"},{"binary_version":"0.76-2","binary_name":"putty-tools"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-36367.json"}}],"schema_version":"1.7.3","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N"},{"type":"Ubuntu","score":"medium"}]}