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CVE-2026-45309 high CVSS 7.5

Path Traversal in asyncssh (CVE-2026-45309)

Summary

Path traversal in asyncssh (CVE-2026-45309). Data can be tampered with by attackers. Exploitable via AuthorizedKeysFile. Mitigation: upgrade to 2.23.0 or later.

Original description

The description as published by the source.

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 authentic…

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-45309 has been found in asyncssh.
Attackers can target a specific entry point like AuthorizedKeysFile over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 7.5/10.
What to do: upgrade asyncssh to 2.23.0 or later.
If unsure, ask your IT team or search "asyncssh CVE-2026-45309" on the vendor's site.

CVE-2026-45309 (asyncssh) — CWE-22 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: AuthorizedKeysFile / af5a81e669633d83d535163f93b6bf3f957c9238 / sshd_config / victim
Patched: 2.23.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

Path traversal (CWE-22) exists in asyncssh. Attackers reach the vulnerable code path via AuthorizedKeysFile without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of asyncssh. Attack surface: AuthorizedKeysFile / af5a81e669633d83d535163f93b6bf3f957c9238 / sshd_config / victim.

🔥 Severity

Severity: High (CVSS 7.5/10). Data can be tampered with by attackers.

🔧 How to fix

Update to 2.23.0.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'asyncssh' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'asyncssh' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で asyncssh を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade asyncssh to 2.23.0

    ステージング環境で 2.23.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

pip asyncssh
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.23.0"}]}]
PyPI asyncssh
[{"type":"ECOSYSTEM","events":[{"introduced":"2.22.0"},{"fixed":"2.23.0"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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