CVE-2026-31517

/* * PoC Concept for CVE-2026-31517 * This code attempts to trigger the IP-TFS reassembly panic. * It requires a system with IP-TFS configured and active. * The PoC sends a sequence of fragmented packets where the first * triggers zero-copy (non-linear) and the second triggers the slow path. */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <arpa/inet.h> #include <sys/socket.h> #include <linux/ip.h> // Note: Actual trigger requires specific IP-TFS encapsulation and protocol handling. // This is a structure to represent the logic of sending crafted fragments. int main() { int sock; char buffer[1024]; struct sockaddr_in dest_addr; // Create raw socket (requires root/capabilities) sock = socket(AF_INET, SOCK_RAW, IPPROTO_RAW); if (sock < 0) { perror("Socket creation failed"); return 1; } dest_addr.sin_family = AF_INET; dest_addr.sin_port = 0; inet_pton(AF_INET, "127.0.0.1", &dest_addr.sin_addr); printf("[+] Sending crafted fragments to trigger skb_put panic on non-linear skb...\n"); // Fragment 1: Designed to trigger zero-copy path in iptfs_reassem_cont // making the skb non-linear. // send_crafted_fragment(sock, ...); // Fragment 2: Designed to hit the slow path, forcing skb_put() on the // non-linear skb created by Fragment 1. // send_crafted_fragment(sock, ...); printf("[+] Payload sent. Check kernel logs for panic/Oops.\n"); close(sock); return 0; }

{"cve": {"id": "CVE-2026-31517", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-22T14:16:51.273", "lastModified": "2026-04-28T16:35:29.403", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: iptfs: fix skb_put() panic on non-linear skb during reassembly\n\nIn iptfs_reassem_cont(), IP-TFS attempts to append data to the new inner\npacket 'newskb' that is being reassembled. First a zero-copy approach is\ntried if it succeeds then newskb becomes non-linear.\n\nWhen a subsequent fragment in the same datagram does not meet the\nfast-path conditions, a memory copy is performed. It calls skb_put() to\nappend the data and as newskb is non-linear it triggers\nSKB_LINEAR_ASSERT check.\n\n Oops: invalid opcode: 0000 [#1] SMP NOPTI\n [...]\n RIP: 0010:skb_put+0x3c/0x40\n [...]\n Call Trace:\n <IRQ>\n iptfs_reassem_cont+0x1ab/0x5e0 [xfrm_iptfs]\n iptfs_input_ordered+0x2af/0x380 [xfrm_iptfs]\n iptfs_input+0x122/0x3e0 [xfrm_iptfs]\n xfrm_input+0x91e/0x1a50\n xfrm4_esp_rcv+0x3a/0x110\n ip_protocol_deliver_rcu+0x1d7/0x1f0\n ip_local_deliver_finish+0xbe/0x1e0\n __netif_receive_skb_core.constprop.0+0xb56/0x1120\n __netif_receive_skb_list_core+0x133/0x2b0\n netif_receive_skb_list_internal+0x1ff/0x3f0\n napi_complete_done+0x81/0x220\n virtnet_poll+0x9d6/0x116e [virtio_net]\n __napi_poll.constprop.0+0x2b/0x270\n net_rx_action+0x162/0x360\n handle_softirqs+0xdc/0x510\n __irq_exit_rcu+0xe7/0x110\n irq_exit_rcu+0xe/0x20\n common_interrupt+0x85/0xa0\n </IRQ>\n <TASK>\n\nFix this by checking if the skb is non-linear. If it is, linearize it by\ncalling skb_linearize(). As the initial allocation of newskb originally\nreserved enough tailroom for the entire reassembled packet we do not\nneed to check if we have enough tailroom or extend it."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-401"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14.1", "versionEndExcluding": "6.18.21", "matchCriteriaId": "8BA62FCD-8829-4508-AFE2-0C12960267CD"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.11", "matchCriteriaId": "4CA2E747-A9EC-4518-9AA2-B4247FC748B7"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:6.14:-:*:*:*:*:*:*", "matchCriteriaId": "7DE421BA-0600-4401-A175-73CAB6A6FB4E"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*", "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*", "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*", "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*", "matchCriteriaId": "512EE3A8-A590-4501-9A94-5D4B268D6138"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/0b352f83cabfefdaafa806d6471f0eca117dc7d5", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/33a7b36268933c75bdc355e5531951e0ea9f1951", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/7fdfe8f6efeb0e1200e22a903f2471539f54522b", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}