CVE-2026-41509

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <stdint.h> // Mocking the vulnerable function signature for demonstration // In the real library, this is part of crypto_sign_open int vulnerable_crypto_sign_open(const unsigned char *sm, size_t smlen) { size_t mlen; // Simulate the underflow condition // If the input header implies a smaller length than the overhead, mlen underflows size_t overhead = 100; if (smlen < overhead) { mlen = smlen - overhead; // Integer underflow occurs here printf("Debug: mlen underflowed to: %zu\n", mlen); // This large mlen is then used in a memcpy, causing buffer overflow unsigned char buffer[64]; // This line would crash or corrupt memory due to huge size // memcpy(buffer, sm + overhead, mlen); return -1; // Vulnerability triggered } return 0; } int main() { // Crafted payload with length less than the expected overhead to trigger underflow size_t malicious_len = 50; unsigned char *payload = (unsigned char *)malloc(malicious_len); memset(payload, 'A', malicious_len); printf("Sending PoC for CVE-2026-41509...\n"); if (vulnerable_crypto_sign_open(payload, malicious_len) == -1) { printf("Vulnerability triggered: Integer underflow leads to potential buffer overflow.\n"); } free(payload); return 0; }

{"cve": {"id": "CVE-2026-41509", "sourceIdentifier": "[email protected]", "published": "2026-05-08T14:16:34.287", "lastModified": "2026-05-12T14:15:13.230", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "CROSS implementation contains reference and optimized implementations of the CROSS post-quantum signature algorithm. Prior to commit fc6b7e7, there is a buffer overflow in crypto_sign_open() caused by an underflow of the integer mlen. This issue has been patched via commit fc6b7e7."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/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": 6.9, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "LOW", "vulnAvailabilityImpact": "LOW", "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:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-121"}, {"lang": "en", "value": "CWE-122"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:cross-crypto:cross-implementation:*:*:*:*:*:*:*:*", "versionEndExcluding": "2026-03-23", "matchCriteriaId": "AF8261C2-70B3-4B9E-9FAD-719A58117870"}]}]}], "references": [{"url": "https://github.com/CROSS-signature/CROSS-implementation/commit/fc6b7e78cdf789bb5c395a81dc601356f1383da0", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/CROSS-signature/CROSS-implementation/security/advisories/GHSA-w72c-hgx8-p7cv", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}