AsyncSSH Rogue Extension Negotiation

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS

• CVE-2023-46445: 0.59% estimated exploitation activity in the next 30 days; percentile 48.09 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary An issue in AsyncSSH v2.14.0 and earlier allows attackers to control the extension info message (RFC 8308) via a man-in-the-middle attack. Details The rogue extension negotiation attack targets an AsyncSSH client connecting to any SSH server sending an extension info message. The attack exploits an implementation flaw in the AsyncSSH implementation to inject an extension info message chosen by the attacker and delete the original extension info message, effectively replacing it. A correct SSH implementation should not process an unauthenticated extension info message. However, the injected message is accepted due to flaws in AsyncSSH. AsyncSSH supports the server-sig-algs and global-requests-ok extensions. Hence, the attacker can downgrade the algorithm used for client authentication by meddling with the value of server-sig-algs (e.g. use of SHA-1 instead of SHA-2). PoC <details <summaryAsyncSSH Client 2.14.0 (simpleclient.py example) connecting to AsyncSSH Server 2.14.0…

Published by the source

9 Nov 2023, 18:34 UTC

Last modified by the source

8 Jul 2026, 06:53 UTC

Source last checked

26 Oct 2026, 13:35 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-cfc2-wr2v-gxm5

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-cfc2-wr2v-gxm5

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# Patch Next advisory brief: CVE-2023-46445

Advisory: AsyncSSH Rogue Extension Negotiation
IDs: CVE-2023-46445, GHSA-cfc2-wr2v-gxm5
Record: https://patchnext.com/advisories/cve-2023-46445 (revision 2, source checked 26 Oct 2026, 13:35 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: asyncssh 2.14.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI asyncssh: affected < 2.14.1; fixed in 2.14.1

## Suggested inspection (read-only)
- `python -m pip show asyncssh`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on asyncssh.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-cfc2-wr2v-gxm5 (OSV record GHSA-cfc2-wr2v-gxm5 lists affected ranges: PyPI asyncssh >=0 <2.14.1 (fixed))
- Verified: https://github.com/advisories/GHSA-cfc2-wr2v-gxm5 (GitHub-reviewed advisory GHSA-cfc2-wr2v-gxm5 lists affected ranges: PyPI asyncssh >=0 <2.14.1)

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