How severe is CVE-2026-45309?

No CVSS score has been assigned to CVE-2026-45309 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-45309?

CVE-2026-45309 affects the following packages: asyncssh (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-45309?

Update asyncssh to 2.23.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45309 is resolved across your whole dependency graph.

How do I detect CVE-2026-45309 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for asyncssh, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-45309 if there is no patch (or I can't update yet)?

Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Is CVE-2026-45309 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-45309 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-45309?

CVE-2026-45309 has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 47th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-45309?

CVE-2026-45309 is classified as Path Traversal (CWE-22). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-45309 published, and has it been updated?

CVE-2026-45309 was published on July 17, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2026-45309 — asyncssh

Fix: ronf/asyncssh@2af2382

CVE-2026-45309 is a Path Traversal vulnerability in asyncssh. A fix is available for asyncssh — see the affected versions and patch details below.

AsyncSSH `AuthorizedKeysFile %u` path traversal allows attacker-selected authorized keys to authenticate a traversal username

Also known asGHSA-g794-3fmp-753hPYSEC-2026-2384

Published

Jul 17, 2026

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-45309.

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs47th percentile — riskier than 47% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍asyncssh

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Summary

AsyncSSH 2.22.0 expands the OpenSSH-compatible AuthorizedKeysFile %u token with the raw SSH username during pre-authentication server config reload. A server configured with a documented per-user key pattern such as AuthorizedKeysFile authorized_keys/%u can be made to read an authorized-keys file outside the intended directory when the SSH username contains path traversal segments. If the attacker can place or reference a readable authorized-keys-format file containing their public key, the attacker can authenticate over SSH as the traversal username.

Affected Product

Package: asyncssh
Ecosystem: pip
Affected versions: confirmed on 2.22.0; exact lower bound not finalized
Tested version: 2.22.0
Audit commit/tag: tag v2.22.0, commit af5a81e669633d83d535163f93b6bf3f957c9238
PyPI sdist SHA256: c3ce72b01be4f97b40e62844dd384227e5ff5a401a3793007c42f86a5c8eb537

Vulnerability Details

CWE: CWE-22: Improper Limitation of a Pathname to a Restricted Directory
Component: AsyncSSH server config reload and public-key authentication (asyncssh/config.py, asyncssh/connection.py, asyncssh/auth_keys.py, asyncssh/misc.py)
Root cause: %u in AuthorizedKeysFile is expanded from the remote username without rejecting path separators or .. segments, and the resulting path is opened without constraining it to the intended authorized-keys directory.
Security boundary violated: the configured authorized-keys directory and public-key authentication trust boundary.
Direct impact: public-key authentication succeeds using an attacker-selected authorized-keys file outside the intended directory.
Chain impact, if any: none claimed; direct authentication impact is primary.

Attack Preconditions

The AsyncSSH server uses a config or equivalent pattern where AuthorizedKeysFile contains %u, for example AuthorizedKeysFile authorized_keys/%u.
Public-key authentication is enabled.
The attacker can place or reference a readable authorized-keys-format file outside the intended directory, such as a file in a world-writable or application-writable location.
The application does not separately reject usernames containing /, \, or .. before AsyncSSH uses the username for key-file selection.

Reproduction

The run-scoped evidence contains a safe localhost proof:

Start the proof harness saved at harness_app.py
Run exploit_proof.py through run_proof.sh
The harness creates sshd_config with AuthorizedKeysFile authorized_keys/%u, writes the attacker's public key to a file outside authorized_keys/, starts a real AsyncSSH server, and attempts two SSH logins.
Expected result: the normal username victim fails, while the traversal username authenticates with the same attacker key.

Observed proof output:

[CONTROL] username=victim success=False
[ATTACK] username=../../../asyncssh-proof-exploit-proof-8b2bd23daeeb.pub success=True
[ATTACK] output=AUTH_BYPASS_SUCCESS username=../../../asyncssh-proof-exploit-proof-8b2bd23daeeb.pub
PASS: traversal username authenticated with attacker-controlled authorized_keys file

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`asyncssh`	≥ 2.22.0&&< 2.23.0	2.23.0`pip install --upgrade 'asyncssh==2.23.0'`

Affected Products

1 product · 1 configurations

Application

asyncsshasyncssh_project

< 2.23.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for asyncssh, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update asyncssh to 2.23.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45309 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Frequently Asked Questions

## Summary AsyncSSH 2.22.0 expands the OpenSSH-compatible `AuthorizedKeysFile` `%u` token with the raw SSH username during pre-authentication server config reload. A server configured with a documented per-user key pattern such as `AuthorizedKeysFile authorized_keys/%u` can be made to read an authorized-keys file outside the intended directory when the SSH username contains path traversal segments. If the attacker can place or reference a readable authorized-keys-format file containing their public key, the attacker can authenticate over SSH as the traversal username. ## Affected Product - Pa

O3 Security · Impact-Aware SCA

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