FreeRDP IMA-ADPCM/MS-ADPCM音频解码器size_t下溢漏洞 (CVE-2026-31883)

/* * CVE-2026-31883 PoC - FreeRDP IMA-ADPCM/MS-ADPCM Integer Underflow * This PoC demonstrates the size_t underflow in audio decoder * Target: FreeRDP < 3.24.0 * * Note: This is a conceptual PoC for educational purposes only. * Author: [email protected] */ #include <stdint.h> #include <stddef.h> #include <stdio.h> /* Simulated IMA-ADPCM decoder state */ struct IMA_ADPCM_Decoder { uint8_t* output_buffer; size_t output_size; size_t output_pos; }; /* Vulnerable function - IMA-ADPCM block parsing */ void ima_adpcm_decode_block_vulnerable( struct IMA_ADPCM_Decoder* decoder, uint8_t* block_data, size_t block_size, size_t nBlockAlign ) { size_t size = block_size; size_t block_header_size = 4; /* IMA-ADPCM block header is 4 bytes */ /* VULNERABLE: No underflow check before subtraction */ while (size > 0) { /* Check if we need to read block header */ if (size % nBlockAlign == 0) { /* Parse block header - this is where underflow occurs */ /* When size < block_header_size, subtraction underflows */ size -= block_header_size; /* size_t underflow here! */ /* Skip header data */ block_data += block_header_size; } /* Decode audio sample */ if (decoder->output_pos < decoder->output_size) { decoder->output_buffer[decoder->output_pos++] = *block_data++; } /* VULNERABLE: This loop runs astronomical number of times */ /* due to size being ~SIZE_MAX after underflow */ size--; } } /* Fixed version with underflow check */ void ima_adpcm_decode_block_fixed( struct IMA_ADPCM_Decoder* decoder, uint8_t* block_data, size_t block_size, size_t nBlockAlign ) { size_t size = block_size; size_t block_header_size = 4; /* FIXED: Add underflow check */ while (size > 0) { if (size % nBlockAlign == 0) { /* Check for underflow before subtraction */ if (size < block_header_size) { /* Handle error condition */ fprintf(stderr, "Error: Insufficient data for block header\n"); break; } size -= block_header_size; block_data += block_header_size; } if (decoder->output_pos < decoder->output_size) { decoder->output_buffer[decoder->output_pos++] = *block_data++; } size--; } } /* PoC trigger condition: * When nBlockAlign is set such that: * 1. size % nBlockAlign == 0 (triggers header parsing) * 2. size < block_header_size (causes underflow) * * Example: block_size = 2, nBlockAlign = 2, block_header_size = 4 * Then: 2 % 2 = 0, and 2 - 4 = underflow to ~SIZE_MAX */ int main(void) { printf("CVE-2026-31883 PoC - FreeRDP Audio Decoder Underflow\n"); printf("Target: FreeRDP < 3.24.0\n"); printf("Vulnerability: size_t underflow in IMA-ADPCM decoder\n\n"); printf("Trigger condition:\n"); printf("- Set nBlockAlign so that size %% nBlockAlign == 0\n"); printf("- Make sure size < block_header_size (4 or 8 bytes)\n"); printf("- This causes: size -= block_header_size to underflow\n\n"); printf("Example attack scenario:\n"); printf("1. Attacker sets up malicious RDP server\n"); printf("2. Server sends crafted RDPSND audio packet\n"); printf("3. nBlockAlign = 2, block_size = 2 triggers underflow\n"); printf("4. Decoder enters infinite-like loop\n"); printf("5. Heap buffer overflow occurs\n"); return 0; }