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PatchSiren cyber security CVE debrief

CVE-2026-5263 wolfSSL CVE debrief

A vulnerability was discovered in wolfSSL, a popular cryptographic library, where URI nameConstraints from constrained intermediate Certificate Authorities (CAs) are parsed but not enforced during certificate chain verification. This issue, tracked as CVE-2026-5263, allows a compromised or malicious sub-CA to issue leaf certificates with URI Subject Alternative Name (SAN) entries that violate the nameConstraints of the issuing CA. As a result, wolfSSL would accept these certificates as valid, potentially leading to security risks. The Common Vulnerability Scoring System (CVSS) score for this vulnerability is 7, indicating a high severity level. The issue was first published on April 9, 2026, and last modified on July 2, 2026.

Vendor
wolfSSL
Product
Unknown
CVSS
HIGH 7
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-09
Original CVE updated
2026-07-02
Advisory published
2026-04-09
Advisory updated
2026-07-02

Who should care

Organizations and developers using wolfSSL for cryptographic operations, especially those relying on certificate chain verification for secure communication, should be aware of this vulnerability. This includes but is not limited to, sectors that heavily depend on secure data transmission such as finance, healthcare, and government. Given the high severity of this issue, immediate attention is advised to ensure the security of their cryptographic infrastructure.

Technical summary

The vulnerability is located in the wolfcrypt/src/asn.c file of the wolfSSL library. Specifically, the issue arises from the incomplete enforcement of URI nameConstraints during certificate chain verification. When a certificate chain includes a constrained intermediate CA, wolfSSL correctly parses the nameConstraints but fails to enforce them on the URI SAN entries of leaf certificates issued by that intermediate CA. This oversight could allow malicious or compromised intermediate CAs to bypass intended security policies, potentially leading to impersonation or other certificate-based attacks.

Defensive priority

High priority should be given to updating wolfSSL to a version that addresses this vulnerability. In the interim, defenders should review their certificate infrastructure to identify any potential misuse of certificates that could exploit this weakness. Implementing additional monitoring and validation of certificate chains may provide temporary mitigation until a patch can be applied.

Recommended defensive actions

  • Update wolfSSL to the latest version that includes a fix for CVE-2026-5263.
  • Review and audit certificate chains and issuing CAs for potential anomalies.
  • Implement additional validation checks for certificate chains in critical systems.
  • Monitor for unusual certificate issuance or validation activities.
  • Consider temporary compensating controls such as stricter certificate validation policies.

Evidence notes

The CVE-2026-5263 record and associated details were obtained from the National Vulnerability Database (NVD) and wolfSSL's official sources. The information provided indicates a high severity vulnerability that requires immediate attention. However, specific details about the exact nature of the nameConstraints bypass and potential exploits are limited in the provided source corpus.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-5263 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-5263

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-5263 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-5263

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.