Path traversal in AsyncSSH - CVE-2026-54590
Published: October 5, 2026
Vulnerability identifier: #VU153256
CSH Severity: Medium
CVSS v4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-54590
CWE-ID: CWE-22
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to authenticate as another user.
The vulnerability exists due to improper limitation of a pathname to a restricted directory in AuthorizedKeysFile %u username substitution when processing SSH authentication requests with crafted usernames. A remote attacker can supply a username beginning with ~ to authenticate as another user.
Exploitation requires %u to be the leading path component and a readable authorized-keys file containing the attacker's key to be reachable in the redirected home directory.
Affected software
AsyncSSH
Fedora
python-asyncssh
Fedora
python-asyncssh
How to mitigate CVE-2026-54590
Install security update from vendor's website.
AsyncSSH - update to 2.23.1
python-asyncssh - addressed in versions 2.23.1-1.fc43, 2.24.0-1.fc44, 2.24.0-2.el10_3
python-asyncssh - addressed in versions 2.23.1-1.fc43, 2.24.0-1.fc44, 2.24.0-2.el10_3