# CVE-2026-90623: andreashappe cochise SSH Host Key ssh_connection.py asyncssh.connect certificate validation

> An attacker can bypass SSH host key validation in the cochise library, enabling man-in-the-middle attacks against remote connections.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Sep 2026
- **Updated:** 14 Sep 2026
- **Also known as:** GHSA-2w8j-c6w5-f5gp

## What is CVE-2026-90623?

CVE-2026-90623 is a medium-severity vulnerability in andreashappe cochise, published on 14 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A weakness has been identified in andreashappe cochise up to 0.4.1. Affected is the function asyncssh.connect of the file src/cochise/ssh_connection.py of the component SSH Host Key Handler. Executing a manipulation can lead to improper certificate validation. The attack may be launched remotely. The attack requires a high level of complexity. The exploitability is told to be difficult. The exploit has been made available to the public and could be used for attacks. The project was informed of the problem early through an issue report but has not responded yet.

Weakness: CWE-295 (Improper Certificate Validation), CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-90623?


## How do I fix CVE-2026-90623?

No fix has been published for CVE-2026-90623 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-90623 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-90623 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90623 and fix it if it is affected.

What it is: CVE-2026-90623 is a medium-severity vulnerability in andreashappe cochise, published on 14 Sep 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-2026-90623 exists.

Affected product: andreashappe cochise. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-90623/ (Markdown: https://insights.sbomify.com/CVE-2026-90623/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90623
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90623
- OSV: https://osv.dev/vulnerability/CVE-2026-90623

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90623/
Summaries are generated and may contain mistakes; the official description above is the record.