Medium 5.9Published Jul 8, 2026

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

Updated under an hour ago (Oct 26, 2026, 7:40 PM ET)

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It affects ronf asyncssh. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for ronf asyncssh

Exploited in the last 30 days

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.

CVSS: 5.9 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness (CWE): CWE-22, CWE-639
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Jul 10, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

ronf asyncssh ronf:asyncssh (from the name)	before 2.23.1	CNA record

References

References

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

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.