CVE-2026-54591
HighCVSS 8.1Exploitation Probability (EPSS)
Low risk24th percentile - higher than 24% of all known CVEs
Summary
A vulnerability in AsyncSSH prior to version 2.23.1 allows a malicious SSH server to write arbitrary files on the SCP client's filesystem. This occurs because _parse_cd_args in scp.py returns server-provided filenames verbatim and _recv_files joins them to the destination path without enforcing the target directory boundary, enabling ../ traversal sequences.
Risk Assessment
An attacker-controlled SSH server can overwrite or create arbitrary files on the client system, potentially leading to application compromise, configuration modification, or malicious code injection.
Recommendation
Upgrade AsyncSSH to version 2.23.1 or later immediately, which fixes the issue by preventing directory traversal during SCP operations.
Other vulnerabilities in AsyncSSH
See all- CVE-2026-45309High
Vulnerability in AsyncSSH before version 2.23.0 allows an attacker to exploit the %u token expansion in AuthorizedKeysFile to read key files outside the intended directory using path traversal segments (/, \, ..). The attacker can authenticate using a chosen key file.
- CVE-2026-54590Medium
AsyncSSH version 2.23.0 contains an incomplete fix for CVE-2026-45309 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.
Original NVD description (English source)
AsyncSSH is a Python package which provides an asynchronous client and server implementation of the SSHv2 protocol on top of the Python asyncio framework. Prior to 2.23.1, a malicious SSH server can write arbitrary files on the asyncssh SCP client's filesystem by sending filenames containing ../ traversal sequences because _parse_cd_args in scp.py returns server-provided names verbatim and _recv_files joins them to the destination path without enforcing the target directory boundary. This issue is fixed in version 2.23.1.