CVE-2026-54590

AsyncSSH AuthorizedKeysFile username substitution bypass through ~ and environment expansion

State: Published
Severity: 5.9 Medium
Published: Jul 8, 2026
Updated: Jul 10, 2026
Reserved: Jun 15, 2026

Description

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.

Scores

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

Weaknesses

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

Affected Products

Product	Versions
asyncsshronf	< 2.23.1Affected

References

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