CVE-2026-8257

// PoC for CVE-2026-8257: Assertion Failure in IRBuilder::makeBrOn // This PoC demonstrates triggering the assertion via a crafted WASM module. // Reference: https://github.com/HackC0der/CVE-Repos/blob/main/wasm-binaryen/... #include <iostream> #include <vector> #include <fstream> // Mock function to simulate the parsing behavior void trigger_vulnerability(const std::vector<char>& wasm_data) { // In the real scenario, Binaryen parses the data. // The specific byte sequence causes 'makeBrOn' to hit an assert. std::cout << "Parsing WASM data..." << std::endl; // Vulnerability logic simulation: // If specific BrOn instruction pattern is found: bool is_malicious_pattern = true; if (is_malicious_pattern) { // This triggers the assertion failure in the vulnerable code std::cerr << "Assertion failed: Invalid type in BrOn instruction." << std::endl; // abort(); // In real exploit, this crashes the compiler } } int main() { // Placeholder for the actual crafted WASM bytes found in the exploit PoC std::vector<char> crafted_wasm = {0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00}; std::cout << "Attempting to trigger CVE-2026-8257..." << std::endl; trigger_vulnerability(crafted_wasm); return 0; }

{"cve": {"id": "CVE-2026-8257", "sourceIdentifier": "[email protected]", "published": "2026-05-11T02:16:27.090", "lastModified": "2026-05-11T02:16:27.090", "vulnStatus": "Received", "cveTags": [], "descriptions": [{"lang": "en", "value": "A vulnerability was detected in WebAssembly Binaryen up to 117. This issue affects the function IRBuilder::makeBrOn of the file src/wasm/wasm-ir-builder.cpp of the component BrOn Parser. Performing a manipulation results in reachable assertion. The attack needs to be approached locally. The exploit is now public and may be used. The patch is named 1251efbc1ea471c1311d2726b2bbe061ff2a291c. It is suggested to install a patch to address this issue."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P/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": 1.9, "baseSeverity": "LOW", "attackVector": "LOCAL", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "LOW", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "LOW", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "PROOF_OF_CONCEPT", "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:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L", "baseScore": 3.3, "baseSeverity": "LOW", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "LOW"}, "exploitabilityScore": 1.8, "impactScore": 1.4}], "cvssMetricV2": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "2.0", "vectorString": "AV:L/AC:L/Au:S/C:N/I:N/A:P", "baseScore": 1.7, "accessVector": "LOCAL", "accessComplexity": "LOW", "authentication": "SINGLE", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "PARTIAL"}, "baseSeverity": "LOW", "exploitabilityScore": 3.1, "impactScore": 2.9, "acInsufInfo": false, "obtainAllPrivilege": false, "obtainUserPrivilege": false, "obtainOtherPrivilege": false, "userInteractionRequired": false}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-617"}]}], "references": [{"url": "https://github.com/HackC0der/CVE-Repos/blob/main/wasm-binaryen/Assertion_Failure_isRef_wasm_Type_getHeapType_commit_3ef8d19", "source": "[email protected]"}, {"url": "https://github.com/WebAssembly/binaryen/", "source": "[email protected]"}, {"url": "https://github.com/WebAssembly/binaryen/commit/1251efbc1ea471c1311d2726b2bbe061ff2a291c", "source": "[email protected]"}, {"url": "https://github.com/WebAssembly/binaryen/issues/8633", "source": "[email protected]"}, {"url": "https://github.com/WebAssembly/binaryen/pull/8635", "source": "[email protected]"}, {"url": "https://vuldb.com/submit/809552", "source": "[email protected]"}, {"url": "https://vuldb.com/vuln/362554", "source": "[email protected]"}, {"url": "https://vuldb.com/vuln/362554/cti", "source": "[email protected]"}]}}