{"id":"UBUNTU-CVE-2021-33500","details":"PuTTY before 0.75 on Windows allows remote servers to cause a denial of service (Windows GUI hang) by telling the PuTTY window to change its title repeatedly at high speed, which results in many SetWindowTextA or SetWindowTextW calls. NOTE: the same attack methodology may affect some OS-level GUIs on Linux or other platforms for similar reasons.","modified":"2026-05-20T16:05:02.284663521Z","published":"2021-05-21T20:15:00Z","upstream":["CVE-2021-33500"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2021-33500"},{"type":"REPORT","url":"https://docs.ssh-mitm.at/puttydos.html"},{"type":"REPORT","url":"https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html"},{"type":"REPORT","url":"https://github.com/ssh-mitm/ssh-mitm-plugins/blob/main/ssh_mitm_plugins/ssh/putty_dos.py"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2021-33500"}],"affected":[{"package":{"name":"putty","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/putty?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_name":"putty","binary_version":"0.67-3+deb9u1build0.16.04.1"},{"binary_name":"putty-tools","binary_version":"0.67-3+deb9u1build0.16.04.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-33500.json"}},{"package":{"name":"putty","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/putty?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_name":"putty","binary_version":"0.70-4"},{"binary_name":"putty-tools","binary_version":"0.70-4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-33500.json"}},{"package":{"name":"putty","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/putty?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_name":"putty","binary_version":"0.73-2"},{"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-2021-33500.json"}},{"package":{"name":"putty","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/putty?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_name":"putty","binary_version":"0.76-2"},{"binary_name":"putty-tools","binary_version":"0.76-2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-33500.json"}},{"package":{"name":"putty","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/putty?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.78-3","0.79-1","0.80-1","0.80-1build2","0.80-1build3","0.81-1"],"ecosystem_specific":{"binaries":[{"binary_name":"pterm","binary_version":"0.81-1"},{"binary_version":"0.81-1","binary_name":"putty"},{"binary_version":"0.81-1","binary_name":"putty-tools"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-33500.json"}},{"package":{"name":"putty","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/putty?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.83-2","0.83-3"],"ecosystem_specific":{"binaries":[{"binary_version":"0.83-3","binary_name":"pterm"},{"binary_version":"0.83-3","binary_name":"putty"},{"binary_name":"putty-tools","binary_version":"0.83-3"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-33500.json"}},{"package":{"name":"putty","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/putty?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.83-3","0.83-3build1"],"ecosystem_specific":{"binaries":[{"binary_version":"0.83-3build1","binary_name":"pterm"},{"binary_name":"putty","binary_version":"0.83-3build1"},{"binary_version":"0.83-3build1","binary_name":"putty-tools"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-33500.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"Ubuntu","score":"low"}]}