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CVE-2026-54590— AsyncSSH AuthorizedKeysFile username substitution bypass through ~ and environment expansion

Quick assessment

Affected
ronf asyncssh
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Ron Frederick AsyncSSH是Ron Frederick个人开发者的一款异步SSH协议库。 AsyncSSH 2.23.1之前版本存在安全漏洞，该漏洞源于AuthorizedKeysFile路径处理中不完整的修复，未能阻止前导~或${ENV}扩展，导致绕过预期的授权密钥目录限制。

CVSS 5.9 · Medium EPSS 0.39% · P33

Possible ATT&CK Techniques 1 AI

T1133 · External Remote Services

Affected Version Matrix 1

VendorProduct Version RangeStatus
ronf asyncssh < 2.23.1 affected
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I. Basic Information for CVE-2026-54590

Vulnerability Information
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Vulnerability Title
AsyncSSH AuthorizedKeysFile username substitution bypass through ~ and environment expansion
Source: CVE Program / CVE List V5
Vulnerability 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 ${ENV}, allowing later expansion in _expand_val and Path(filename).expanduser() to escape the intended authorized-keys directory. This issue is fixed in version 2.23.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对路径名的限制不恰当(路径遍历)
Source: CVE Program / CVE List V5
Vulnerability Title
Ron Frederick AsyncSSH 路径遍历漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Ron Frederick AsyncSSH是Ron Frederick个人开发者的一款异步SSH协议库。 AsyncSSH 2.23.1之前版本存在安全漏洞，该漏洞源于AuthorizedKeysFile路径处理中不完整的修复，未能阻止前导~或${ENV}扩展，导致绕过预期的授权密钥目录限制。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
ronf asyncssh < 2.23.1 -

II. Public POCs for CVE-2026-54590

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III. Intelligence Information for CVE-2026-54590

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Patches & Fixes for CVE-2026-54590 (1)

Vendor Advisories for CVE-2026-54590 (1)

Other References for CVE-2026-54590 (1)

IV. Related Vulnerabilities

Same product: asyncssh
Same vendor: ronf
Same weakness: CWE-22

V. Comments for CVE-2026-54590

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