CVE-2026-54590 PUBLISHED

AsyncSSH AuthorizedKeysFile username substitution bypass through ~ and environment expansion

Assigner: GitHub_M
Reserved: 15.06.2026 Published: 08.07.2026 Updated: 08.07.2026

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.

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS Score: 5.9

Product Status

Vendor ronf
Product asyncssh
Versions
  • Version < 2.23.1 is affected

References

Problem Types

  • CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') CWE
  • CWE-639: Authorization Bypass Through User-Controlled Key CWE