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CVE-2026-54590

AsyncSSH AuthorizedKeysFile username substitution bypass through ~ and environment expansion

Published: Jul 8, 2026Updated: Jul 10, 2026 Sources: CVE List NVDCWE-22
5.9MEDIUM
NVD MITRE
EPSS Score
0.3%
Top 79.3%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
Self-Check
OpenVAS

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:HPR:NUI:NS:UC:NI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:HIntegrity
High
A:NAvailability
None
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Weaknesses

CWE-22CWE-639

Affected Products

ronf
asyncssh

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

3 techniques
Collection
Discovery
Initial Access
View detailed technique mapping

References

https://github.com/ronf/asyncssh/commit/3d515ba9ba0cd9990d248bdf62bcf05d51261a88
github.com
https://github.com/ronf/asyncssh/releases/tag/v2.23.1
github.com
https://github.com/ronf/asyncssh/security/advisories/GHSA-qr67-gv47-xwwh
github.com

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