CVE-2026-5501

What it is

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.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of data exposure, data tampering.

Exploit odds

0.3% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-04-10 04:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 10:59 UTC Last updatedMost recent change to the record

Details

Published

2026-04-10 04:17 UTC

Last modified

2026-06-17 10:59 UTC

Exploit probability

0.3% · EPSS, next 30 days

Weakness

CWE-295 · Improper certificate validation

Record status

Analyzed

Affected

• Wolfssl ≤ 5.9.0

Attack profile CVSS 4.0 · 8.6

Attack vector

Network

Complexity

Low

Attack requirements

None

Privileges needed

Low

User interaction

None

Confidentiality

High

Integrity

High

Availability

None