# CVE-2026-83540: wolfSSHd on Windows race condition leading to logon token reused across connections

> A race condition in wolfSSHd on Windows allows less privileged users to hijack logon tokens and gain access as more privileged users.

- **Severity:** High 7.7 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Oct 2026
- **Updated:** 7 Oct 2026
- **Also known as:** GHSA-36jf-xmwg-5wp8

## What is CVE-2026-83540?

CVE-2026-83540 is a high-severity vulnerability in wolfSSL wolfSSH, published on 7 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

When password or public key authentication is used with the Windows port of wolfSSHd, the Windows logon token acquired for one authenticated connection is not released before a token is acquired for a subsequent connection, resulting in user login poisoning between connections. A less privileged user with a valid account on the server can exploit this to force a login as a more privileged user. The vulnerability was introduced with the initial Windows port of wolfSSHd in wolfSSH version 1.4.15 and affects all versions through 1.5.0. Non-Windows builds of wolfSSHd are not affected.

Weakness: CWE-613 (DEPRECATED: Insufficient Session Expiration), CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-83540?

It affects 1 product.


Products: Wolfssh Wolfssh.

## How do I fix CVE-2026-83540?

No fix has been published for CVE-2026-83540 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-83540 being exploited?

There is no known exploitation of CVE-2026-83540 in the wild and no public exploit code.

## Other vulnerabilities in wolfSSL wolfSSH

- [CVE-2022-32073](https://insights.sbomify.com/CVE-2022-32073/): Integer overflow in n/a (critical 9.8)
- [CVE-2025-14942](https://insights.sbomify.com/CVE-2025-14942/): Authentication Bypass (critical 9.4)
- [CVE-2025-11625](https://insights.sbomify.com/CVE-2025-11625/): Host verification bypass and credential leak (critical 9.4)
- [CVE-2024-2873](https://insights.sbomify.com/CVE-2024-2873/): User authentication bypass in wolfSSH server (critical 9.1)
- [CVE-2026-16516](https://insights.sbomify.com/CVE-2026-16516/): wolfSSH ECDSA host key curve not validated against negotiated algorithm (critical 9.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-83540 and fix it if it is affected.

What it is: CVE-2026-83540 is a high-severity vulnerability in wolfSSL wolfSSH, published on 7 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-83540 in the wild and no public exploit code.

Affected product: wolfSSL wolfSSH. 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-2026-83540/ (Markdown: https://insights.sbomify.com/CVE-2026-83540/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-83540
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-83540
- OSV: https://osv.dev/vulnerability/CVE-2026-83540

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-83540/
Summaries are generated and may contain mistakes; the official description above is the record.