# CVE-2026-45309: AsyncSSH `AuthorizedKeysFile %u` path traversal allows attacker-selected authorized keys to authenticate a traversal username

> Attackers can authenticate using arbitrary key files via path traversal in AsyncSSH when AuthorizedKeysFile uses the %u token.

- **Severity:** High 8.2 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Jul 2026
- **Updated:** 21 Jul 2026
- **Also known as:** CLEANSTART-2026-UM40247, CLEANSTART-2026-WV96741, DEBIAN-CVE-2026-45309, ECHO-478b-8ec8-3dc3, GHSA-g794-3fmp-753h, MINI-4ggg-6rv9-j647, MINI-grhq-q2c4-v2w7, PYSEC-2026-2384, UBUNTU-CVE-2026-45309, openSUSE-SU-2026:11042-1

## What is CVE-2026-45309?

CVE-2026-45309 is a high-severity path traversal vulnerability in ronf asyncssh, published on 17 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-45309?

3 open source packages ship an affected version, including asyncssh. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `asyncssh` | PyPI | From 2.22.0 | 2.23.0 |
| `asyncssh` | PyPI | From 2.22.0 | 2.23.0 |
| `asyncssh` | PyPI | From 2.22.0 | 2.23.0 |
| `python-asyncssh` | openSUSE:Tumbleweed | All versions | 2.23.1-1.1 |

Products: Asyncssh Project Asyncssh.

## How do I fix CVE-2026-45309?

Upgrade asyncssh to 2.23.0 or later.

## Is CVE-2026-45309 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-45309 exists.

## Other vulnerabilities in ronf asyncssh

- [CVE-2018-7749](https://insights.sbomify.com/CVE-2018-7749/): AsyncSSH SSH Server Authentication Bypass (critical 9.8)
- [CVE-2023-46446](https://insights.sbomify.com/CVE-2023-46446/): AsyncSSH Rogue Session Attack (medium 6.8)
- [CVE-2023-46445](https://insights.sbomify.com/CVE-2023-46445/): AsyncSSH Rogue Extension Negotiation (medium 5.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45309 and fix it if it is affected.

What it is: CVE-2026-45309 is a high-severity path traversal vulnerability in ronf asyncssh, published on 17 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-45309 exists.

Affected packages and fixed versions:
- asyncssh (PyPI): affected from 2.22.0; fixed in 2.23.0
- asyncssh (PyPI): affected from 2.22.0; fixed in 2.23.0
- asyncssh (PyPI): affected from 2.22.0; fixed in 2.23.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-45309/ (Markdown: https://insights.sbomify.com/CVE-2026-45309/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45309
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45309
- OSV: https://osv.dev/vulnerability/CVE-2026-45309

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45309/
Summaries are generated and may contain mistakes; the official description above is the record.