---
title: "CVE-2026-45309\n    | Ubuntu"
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2026-45309?format=md
keywords: index, follow
---

# CVE-2026-45309

Publication date 17 July 2026

Last updated 7 August 2026

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**7.5 · High**

[Score breakdown](https://ubuntu.com/security/CVE-2026-45309?format=md#impact-score)

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## 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 2.23.0, AsyncSSH expands the OpenSSH-compatible
AuthorizedKeysFile %u token in asyncssh/config.py, asyncssh/connection.py,
asyncssh/auth\_keys.py, and asyncssh/misc.py with the raw SSH username
during pre-authentication server config reload, allowing a server
configured with AuthorizedKeysFile authorized\_keys/%u to read an
authorized-keys file outside the intended directory when the SSH username
contains /, \, or .. path traversal segments and authenticate with an
attacker-selected key file. This issue is fixed in version 2.23.0.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| python-asyncssh | 26.04 LTS resolute | Needs evaluation |
| 24.04 LTS noble | Needs evaluation |
| 22.04 LTS jammy | Needs evaluation |
| 20.04 LTS focal | Needs evaluation |
| 18.04 LTS bionic | Needs evaluation |
| 16.04 LTS xenial | Needs evaluation |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)

## Severity score breakdown

CVSS version:

CVSS v4.0

[CVSS v4.0](https://ubuntu.com/security/CVE-2026-45309?format=md)
[CVSS v3.0](https://ubuntu.com/security/CVE-2026-45309?format=md)

**Base score**

8.2 · High

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | Low |
  | Attack requirements | Present |
  | Privileges required | None |
  | User interaction | None |
  | Vulnerable system - Confidentiality impact | None |
  | Vulnerable system - Integrity impact | High |
  | Vulnerable system - Availability impact | None |
  | Subsequent system - Confidentiality impact | None |
  | Subsequent system - Integrity impact | None |
  | Subsequent system - Availability impact | None |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 8.2 · High |
  | Base + Threat score | - |
  | Base + Environmental score | - |
  | Base + Threat + Environmental score | - |

**Vector:** 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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-45309)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-45309)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-45309)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-45309)

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-45309>
* <https://github.com/advisories/GHSA-g794-3fmp-753h>