# CVE-2026-5501: Improper Certificate Signature Verification in X.509 Chain Validation Allows Forged Leaf Certificates

> Attackers can bypass certificate validation in wolfSSL's OpenSSL compatibility layer to forge certificates, affecting applications using this specific API.

- **Severity:** High 8.6 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/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:** Yes
- **Published:** 10 Apr 2026
- **Updated:** 22 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-5501, GHSA-hg75-4cmp-f367, JLSEC-2026-730, UBUNTU-CVE-2026-5501

## What is CVE-2026-5501?

CVE-2026-5501 is a high-severity vulnerability in Wolfssl Wolfssl, published on 10 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

wolfSSL_X509_verify_cert in the OpenSSL compatibility layer accepts a certificate chain in which the leaf's signature is not checked, if the attacker supplies an untrusted intermediate with Basic Constraints `CA:FALSE` that is legitimately signed by a trusted root. An attacker who obtains any leaf certificate from a trusted CA (e.g. a free DV cert from Let's Encrypt) can forge a certificate for any subject name with any public key and arbitrary signature bytes, and the function returns `WOLFSSL_SUCCESS` / `X509_V_OK`. The native wolfSSL TLS handshake path (`ProcessPeerCerts`) is not susceptible and the issue is limited to applications using the OpenSSL compatibility API directly, which would include integrations of wolfSSL into nginx and haproxy.

Weakness: CWE-295 (Improper Certificate Validation)

## Which versions are affected by CVE-2026-5501?

It affects 1 product.


Products: Wolfssl Wolfssl.

## How do I fix CVE-2026-5501?

Apply the vendor's patch.

## Is CVE-2026-5501 being exploited?

There is no known exploitation of CVE-2026-5501 in the wild and no public exploit code.

## Other vulnerabilities in Wolfssl Wolfssl

- [CVE-2024-5991](https://insights.sbomify.com/CVE-2024-5991/): Buffer overread in domain name matching (critical 10.0)
- [CVE-2021-37155](https://insights.sbomify.com/CVE-2021-37155/): Security feature bypass in n/a (critical 9.8)
- [CVE-2020-36177](https://insights.sbomify.com/CVE-2020-36177/): Memory corruption in n/a (critical 9.8)
- [CVE-2014-2896](https://insights.sbomify.com/CVE-2014-2896/): Memory corruption in n/a (critical 9.8)
- [CVE-2014-2897](https://insights.sbomify.com/CVE-2014-2897/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-5501 and fix it if it is affected.

What it is: CVE-2026-5501 is a high-severity vulnerability in Wolfssl Wolfssl, published on 10 Apr 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-2026-5501 in the wild and no public exploit code.

Affected product: Wolfssl Wolfssl. 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-2026-5501/ (Markdown: https://insights.sbomify.com/CVE-2026-5501/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-5501
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-5501
- OSV: https://osv.dev/vulnerability/CVE-2026-5501

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-5501/
Summaries are generated and may contain mistakes; the official description above is the record.