# CVE-2026-81535: wolfSSH SSH client accepts unsolicited forwarded-tcpip channel opens without an authorization check

> A malicious SSH peer can trigger unbounded memory allocation and unauthorized channel opens in wolfSSH clients built with forwarding enabled, causing denial of service.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Oct 2026
- **Updated:** 7 Oct 2026
- **Also known as:** GHSA-cqr9-f685-gr3w

## What is CVE-2026-81535?

CVE-2026-81535 is a medium-severity missing authorization vulnerability in wolfSSL Inc. wolfSSH, published on 7 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In wolfSSH through 1.5.0 built with --enable-fwd, DoChannelOpen() in src/internal.c gates only direct-tcpip channel opens with the forwarding policy callback. forwarded-tcpip opens are admitted without an authorization check and are not capped in number, allowing a malicious SSH peer to make an endpoint allocate unbounded per-channel buffers for forwarding channels the application never authorized. A client also does not check a forwarded-tcpip open against the forwards it registered with a tcpip-forward request, as RFC 4254 section 7.2 requires, so a malicious server can open forwarding channels for addresses and ports the client never asked it to forward.

Weakness: CWE-863 (Incorrect Authorization), CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-81535?

It affects 1 product.


Products: Wolfssh Wolfssh.

## How do I fix CVE-2026-81535?

No fix has been published for CVE-2026-81535 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-81535 being exploited?

There is no known exploitation of CVE-2026-81535 in the wild and no public exploit code.

## Other vulnerabilities in wolfSSL Inc. 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-2026-81535 and fix it if it is affected.

What it is: CVE-2026-81535 is a medium-severity missing authorization vulnerability in wolfSSL Inc. wolfSSH, published on 7 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-81535 in the wild and no public exploit code.

Affected product: wolfSSL Inc. 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-2026-81535/ (Markdown: https://insights.sbomify.com/CVE-2026-81535/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-81535
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-81535
- OSV: https://osv.dev/vulnerability/CVE-2026-81535

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-81535/
Summaries are generated and may contain mistakes; the official description above is the record.