Path Traversal in AsyncSSH SCP Client

Publication date: 2026-07-08

Last updated on: 2026-07-08

Assigner: GitHub, Inc.

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. 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.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-07-08

Last Modified

2026-07-08

Generated

2026-07-09

AI Q&A

2026-07-09

EPSS Evaluated

N/A

NVD

CVE-2026-54591

Affected Vendors & Products

Vendor	Product	Version / Range
asyncssh	asyncssh	2.23.1

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-22	The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

Attack-Flow Graph

Executive Summary

This vulnerability exists in the AsyncSSH Python package, which implements the SSHv2 protocol asynchronously. Before version 2.23.1, a malicious SSH server could exploit the SCP client by sending filenames containing directory traversal sequences (../). The client’s _parse_cd_args function returns these server-provided filenames without validation, and _recv_files joins them to the destination path without enforcing directory boundaries. This allows the server to write arbitrary files anywhere on the client’s filesystem.

Impact Analysis

This vulnerability can have serious impacts because it allows a malicious SSH server to write arbitrary files on the client’s filesystem. This can lead to unauthorized modification or creation of files, potentially resulting in data corruption, system compromise, or execution of malicious code. The CVSS score of 8.1 indicates a high severity with impacts on integrity and availability.

Mitigation Strategies

To mitigate this vulnerability, upgrade AsyncSSH to version 2.23.1 or later, where the issue has been fixed.

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