{"id":"CVE-2026-54590","aliases":["GHSA-qr67-gv47-xwwh"],"url":"https://o3.security/vulnerability/CVE-2026-54590","summary":"AsyncSSH AuthorizedKeysFile username substitution bypass through ~ and environment expansion","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. Version 2.23.0 contains an incomplete fix for CVE-2026-45309 in SSHServerConfig._set_tokens that blocks /, , and .. before %u substitution in AuthorizedKeysFile but does not block a leading ~ or ${ENV}, allowing later expansion in _expand_val and Path(filename).expanduser() to escape the intended authorized-keys directory. This issue is fixed in version 2.23.1.","published":"2026-07-08T20:36:45.258Z","modified":"2026-08-12T03:51:37.056125299Z","cvss":{"score":5.9,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"asyncssh","fixedVersion":"2.23.1"}],"fix":{"url":"https://github.com/ronf/asyncssh/commit/3d515ba9ba0cd9990d248bdf62bcf05d51261a88","label":"ronf/asyncssh@3d515ba"},"references":[{"type":"WEB","url":"https://github.com/ronf/asyncssh/releases/tag/v2.23.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54590.json"},{"type":"ADVISORY","url":"https://github.com/ronf/asyncssh/security/advisories/GHSA-qr67-gv47-xwwh"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54590"},{"type":"FIX","url":"https://github.com/ronf/asyncssh/commit/3d515ba9ba0cd9990d248bdf62bcf05d51261a88"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:37.056125299Z"}}