Unauthenticated account access via post-validation path expansion
Published Jul 8, 2026 · Updated Jul 8, 2026
Path traversal in AsyncSSH 2.23.0 allows remote attackers to authenticate as an existing account through a redirected key file. SSHServerConfig._set_tokens checks the remote username before %u substitution, but later environment expansion and Path.expanduser() restore path control. Exploitation requires AuthorizedKeysFile to begin with %u, public-key authentication, an existing target account, and a readable key file containing the attacker's key.
Summary
What happened
Path traversal in AsyncSSH 2.23.0 allows remote attackers to authenticate as an existing account through a redirected key file. SSHServerConfig._set_tokens checks the remote username before %u substitution, but later environment expansion and Path.expanduser() restore path control. Exploitation requires AuthorizedKeysFile to begin with %u, public-key authentication, an existing target account, and a readable key file containing the attacker's key.
The record
- CVE
- CVE-2026-54590
- Published
- Jul 8, 2026
- Updated
- Jul 8, 2026
- Vendor
- Ron Frederick
- Product
- AsyncSSH
- Classifications
- CWE-639, CWE-22, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 8, 2026CVE publishedPublication date reported by the CVE source.
- Jul 8, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 2.23.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- AuthorizedKeysFile expansion in-process proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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