# CVE-2026-5501: wolfSSL improper certificate validation in OpenSSL compatibility layer

Source: https://junglewise.ai/threats/cve-2026-5501-wolfssl-improper-certificate-validation-in-openssl-compatibility  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-10. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

CVE-2026-5501 · Severity: high · CVSS 8.1 · Published 2026-04-10

A security flaw in the wolfSSL library's OpenSSL compatibility layer allows attackers to bypass certificate verification. By using a specially crafted certificate chain, an attacker can impersonate any website or service, potentially leading to intercepted communications or unauthorized access. This affects applications that use wolfSSL to handle secure connections, such as nginx or HAProxy web servers.

Technologies: [Wolfssl](https://junglewise.ai/threats/technologies/wolfssl). Vendors: [Wolfssl](https://junglewise.ai/threats/vendors/wolfssl).

## Quick answers

**Is CVE-2026-5501 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-5501 being exploited in the wild.

**How severe is CVE-2026-5501?** High severity, with a CVSS score of 8.1, published 10 April 2026.

**Which products and versions are affected?** wolfSSL wolfSSL up to and including 5.9.0.

**Is there a fix for CVE-2026-5501?** A patch was published on 2026-04-06: Fixes merged into master branch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-5501 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-5501?** Check whether you run Wolfssl. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A vulnerability exists in the wolfSSL_X509_verify_cert function within the OpenSSL compatibility layer. The root cause is a failure to check the leaf certificate's signature if an attacker provides an untrusted intermediate certificate with the Basic Constraints 'CA:FALSE' that is signed by a trusted root. An attacker with a valid leaf certificate from a trusted CA can forge a new certificate for any subject name and public key. This issue specifically affects the compatibility API and does not impact the native wolfSSL TLS handshake path. The vulnerability was addressed in version 5.9.1.

## Affected products

- wolfSSL wolfSSL up to and including 5.9.0

## Timeline

- 2026-03-30: other: Fixes submitted via pull request
- 2026-04-06: patched: Fixes merged into master branch
- 2026-04-10: disclosed: CVE-2026-5501 published

## References

- [https://github.com/wolfSSL/wolfssl/pull/10102](https://github.com/wolfSSL/wolfssl/pull/10102)

## Related threats

- [wolfSSL certificate validation bypass in ConfirmNameConstraints()](https://junglewise.ai/threats/cve-2026-95208-an-issue-in-the-confirmnameconstraints-function-wolfcrypt-src-asn)
- [wolfSSL revocation check bypass with OCSP and CRL](https://junglewise.ai/threats/cve-2026-94417-when-an-application-enables-both-ocsp-and-crl-revocation-checking)
- [wolfSSL TLS 1.2 ChangeCipherSpec message ordering bypass](https://junglewise.ai/threats/cve-2026-93304-a-d-tls-1-2-client-can-accept-a-changecipherspec-message-before)
- [wolfSSL MatchTrustedPeer public key validation bypass](https://junglewise.ai/threats/cve-2026-93302-matchtrustedpeer-ignores-the-public-key-used-leading-to-forged-ca)
- [wolfSSL TLS authentication bypass in Raw Public Key handling](https://junglewise.ai/threats/cve-2026-89136-when-using-rpk-raw-public-key-the-client-side-of-a-tls-1-2-1-3)