Is CVE-2026-45309 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-45309 being exploited in the wild.

How severe is CVE-2026-45309?

Medium severity, with a CVSS score of 4, published 17 July 2026.

Which products and versions are affected?

asyncssh (PyPI) ECOSYSTEM:introduced=2.22.0,fixed=2.23.0.

Is there a fix for CVE-2026-45309?

Yes. asyncssh (PyPI): upgrade to 2.23.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-45309 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-45309?

Check whether you run asyncssh (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-45309: ronf AsyncSSH path traversal in AuthorizedKeysFile

CVE-2026-45309 · Severity: medium · CVSS 4 · Published 2026-07-17

AsyncSSH is a Python library used to build SSH clients and servers. A security flaw allows attackers to bypass authentication by providing a specially crafted username containing path traversal characters (like "../"). If the server is configured to look up user keys using the %u placeholder, an attacker can trick the system into reading a different file they control, allowing them to log in without a valid password or authorized key.

Technologies: asyncssh (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-45309 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-45309 being exploited in the wild.
How severe is CVE-2026-45309?: Medium severity, with a CVSS score of 4, published 17 July 2026.
Which products and versions are affected?: asyncssh (PyPI) ECOSYSTEM:introduced=2.22.0,fixed=2.23.0.
Is there a fix for CVE-2026-45309?: Yes. asyncssh (PyPI): upgrade to 2.23.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-45309 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-45309?: Check whether you run asyncssh (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

asyncssh (PyPI): upgrade to 2.23.0 or later
```
pip install "asyncssh>=2.23.0"
```

Technical details

A path traversal vulnerability exists in AsyncSSH's handling of the %u token within the AuthorizedKeysFile configuration. When the server reloads configuration or processes public-key authentication, it expands the %u placeholder using the raw, unvalidated SSH username provided by the client. By supplying a username containing path traversal segments (e.g., ../, \, or /), an attacker can force the server to read an authorized-keys file from an unintended location on the filesystem. If the attacker can place or reference a file in a known location that contains their own public key, they can successfully authenticate as the traversal username. This issue is fixed in version 2.23.0 by implementing strict validation for username substitutions.

Affected products

ronf AsyncSSH < 2.23.0

Identifiers

CVE-2026-45309
GHSA-g794-3fmp-753h
PYSEC-2026-2384

Timeline

2026-05-26: advisory: GitHub Security Advisory published
2026-07-17: disclosed: CVE published to NVD
2026-07-17: patched: Fix released in version 2.23.0

References

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