CVE-2026-54590

MEDIUM

AsyncSSH AuthorizedKeysFile username substitution bypass through ~ and environment expansion

Title source: cna
STIX 2.1

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.

References (3)

Core 3

Scores

CVSS v3 5.9
EPSS 0.0029
EPSS Percentile 20.8%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

CISA SSVC

Vulnrichment
Exploitation poc
Automatable no
Technical Impact partial

Details

CWE
CWE-22 CWE-639
Status published
Products (1)
ronf/asyncssh < 2.23.1
Published Jul 08, 2026
Tracked Since Jul 09, 2026