{"id":"UBUNTU-CVE-2026-45309","details":"AsyncSSH is a Python package which provides an asynchronous client and server implementation of the SSHv2 protocol on top of the Python asyncio framework. Prior to 2.23.0, AsyncSSH expands the OpenSSH-compatible AuthorizedKeysFile %u token in asyncssh/config.py, asyncssh/connection.py, asyncssh/auth_keys.py, and asyncssh/misc.py with the raw SSH username during pre-authentication server config reload, allowing a server configured with AuthorizedKeysFile authorized_keys/%u to read an authorized-keys file outside the intended directory when the SSH username contains /, \\, or .. path traversal segments and authenticate with an attacker-selected key file. This issue is fixed in version 2.23.0.","modified":"2026-08-04T11:00:09.510619416Z","published":"2026-07-17T19:17:00Z","upstream":["CVE-2026-45309"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-45309"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-45309"},{"type":"REPORT","url":"https://github.com/advisories/GHSA-g794-3fmp-753h"}],"affected":[{"package":{"name":"python-asyncssh","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/python-asyncssh?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.2.0-1","1.2.1-1","1.3.0-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-asyncssh","binary_version":"1.3.0-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-45309.json"}},{"package":{"name":"python-asyncssh","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/python-asyncssh?arch=source&distro=esm-apps%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.8.1-2","1.11.0-2","1.11.1-1","1.11.1-1ubuntu0.1~esm1","1.11.1-1ubuntu0.1~esm2"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-asyncssh","binary_version":"1.11.1-1ubuntu0.1~esm2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-45309.json"}},{"package":{"name":"python-asyncssh","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/python-asyncssh?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.12.2-1","1.12.2-1ubuntu0.1","1.12.2-1ubuntu0.2"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-asyncssh","binary_version":"1.12.2-1ubuntu0.2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-45309.json"}},{"package":{"name":"python-asyncssh","ecosystem":"Ubuntu:Pro:22.04:LTS","purl":"pkg:deb/ubuntu/python-asyncssh?arch=source&distro=esm-apps%2Fjammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.5.0-1","2.5.0-1ubuntu0.1~esm1","2.5.0-1ubuntu0.1","2.5.0-1ubuntu0.1+esm1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-asyncssh","binary_version":"2.5.0-1ubuntu0.1+esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-45309.json"}},{"package":{"name":"python-asyncssh","ecosystem":"Ubuntu:Pro:24.04:LTS","purl":"pkg:deb/ubuntu/python-asyncssh?arch=source&distro=esm-apps%2Fnoble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.10.1-2","2.10.1-2ubuntu0.1","2.10.1-2ubuntu0.1+esm1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-asyncssh","binary_version":"2.10.1-2ubuntu0.1+esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-45309.json"}},{"package":{"name":"python-asyncssh","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/python-asyncssh?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.20.0-1","2.21.1-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-asyncssh","binary_version":"2.21.1-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-45309.json"}}],"schema_version":"1.8.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"},{"type":"Ubuntu","score":"medium"}]}