What is the CVSS score of EUVD-2026-42399?

EUVD-2026-42399 has a CVSS 3.1 base score of 8.1 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H. EPSS exploitation probability: 0.3%.

Which versions of AsyncSSH are affected by EUVD-2026-42399?

AsyncSSH, a Python library used by applications performing SSH file transfers, contains a path traversal vulnerability (CVE-2026-54591) that allows attackers controlling an SSH server to write…. A patch is available.

Is there a public PoC exploit available for EUVD-2026-42399?

Yes, a public proof-of-concept exploit is available for EUVD-2026-42399. Prioritise patching immediately. EPSS: 0.3%.

How to fix or mitigate EUVD-2026-42399?

Within 24 hours: audit all internal applications and dependencies for AsyncSSH usage and identify affected versions. Within 7 days: restrict SCP operations to connections with whitelisted, internally-controlled SSH servers; notify application teams of the vulnerability. Within 30 days: upgrade AsyncSSH to version 2.23.1 or later in all affected applications and validate thoroughly.

AsyncSSH EUVD-2026-42399

| CVE-2026-54591 HIGH

Path Traversal (CWE-22)

2026-07-08 security-advisories@github.com

GHSA-2wxc-x7rj-hg8f

Python Path Traversal Red Hat

8.1

CVSS 3.1 · Vendor: github

Severity by source

Vendor (github) PRIMARY

8.1 HIGH

AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H

vuln.today AI

8.1 HIGH

Attacker controls the SSH server but the victim must initiate the SCP transfer (UI:R); arbitrary file write yields I:H and A:H, with no data disclosure (C:N).

3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H

4.0 AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N

Red Hat

8.1 HIGH

qualitative

Primary rating from Vendor (github).

CVSS VectorVendor: github

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

None

Integrity

High

Availability

High

Lifecycle Timeline

Patch available

Jul 08, 2026 - 22:04 EUVD

Analysis Generated

Jul 08, 2026 - 21:39 vuln.today

Blast Radius

ecosystem impact

† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth

28 pypi packages depend on asyncssh (9 direct, 19 indirect)

Ecosystem-wide dependent count for version 2.23.1.

DescriptionCVE.org

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.

Articles & Coverage 1

News 10 New Python Vulnerabilities - 2 Critical, 8 High, 1 With POC Jul 09, 2026

AnalysisAI

Arbitrary file write in the AsyncSSH Python library (versions prior to 2.23.1) allows a malicious or compromised SSH server to plant files anywhere on an SCP client's filesystem when a user initiates a file-copy operation against it. Because the SCP client trusts server-supplied filenames verbatim, a hostile server can return names containing ../ sequences to escape the intended download directory, enabling code execution or system tampering. No public exploit has been identified at time of analysis, and the flaw is not listed in CISA KEV.

Technical ContextAI

AsyncSSH implements the SSHv2 protocol (including the SCP subsystem) on top of Python's asyncio framework. The vulnerability is a classic CWE-22 path traversal in the SCP client receive path: _parse_cd_args in scp.py returns the filename provided by the remote server without sanitization, and _recv_files then joins that name to the local destination path without verifying the result stays within the target directory boundary. Since SCP is a server-driven protocol where the sender dictates filenames, a trusted-client / untrusted-server trust inversion lets the server inject '../' components that resolve outside the intended folder. CPE data was not supplied, but the affected component is unambiguously the ronf/asyncssh Python package's SCP client code.

RemediationAI

Vendor-released patch: upgrade AsyncSSH to version 2.23.1 or later, which enforces the destination directory boundary when reconstructing received filenames (fix commit d730803b8e4e94c20c7580d90f94d1e05f9f58de; release https://github.com/ronf/asyncssh/releases/tag/v2.23.1). Until you can upgrade, restrict SCP client usage to trusted, authenticated servers only and avoid initiating AsyncSSH SCP downloads from servers you do not control, since the attack requires connecting to a malicious server; where feasible, run SCP client operations under a low-privilege account and into a dedicated, unprivileged destination directory (with no symlinks and minimal write reach) to blunt the impact of a traversal write, accepting that this does not prevent the traversal itself. Full details are in the advisory at https://github.com/ronf/asyncssh/security/advisories/GHSA-2wxc-x7rj-hg8f.