MLX has Wild Pointer Dereference in load_gguf()
Summary
Segmentation fault in mlx::core::load_gguf() when loading malicious GGUF files. Untrusted pointer from external gguflib library is dereferenced without validation, causing application crash.
Environment:
- OS: Ubuntu 20.04.6 LTS
- Compiler: Clang 19.1.7
Vulnerability
Location: mlx/io/gguf.cpp
- Function
extract_tensor_data() at lines 59-79 - Vulnerable memcpy at lines 64-67
- Called from
load_arrays() at line 177
The Bug:
```cpp
std::tuple<allocator::Buffer, Dtype> extract_tensor_data(gguf_tensor* tensor) {
std::optional<Dtype> equivalent_dtype = gguf_type_to_dtype(tensor->type);
if (equivalent_dtype.has_value()) {
allocator::Buffer buffer = allocator::malloc(tensor->bsize);
memcpy(
buffer.raw_ptr(),
tensor->weights_data, // untrusted pointer from gguflib
tensor->num_weights * equivalent_dtype.value().size());
return {buffer, equivalent_dtype.value()};
}
// ...
}
```
Possible Fix
```cpp
std::tuple<allocator::Buffer, Dtype> extract_tensor_data(gguf_tensor* tensor) {
std::optional<Dtype> equivalent_dtype = gguf_type_to_dtype(tensor->type);
if (equivalent_dtype.has_value()) {
// FIX: Validate pointer
if (!tensor->weights_data) {
throw std::runtime_error("[load_gguf] NULL tensor data pointer");
}
allocator::Buffer buffer = allocator::malloc(tensor->bsize);
memcpy(
buffer.raw_ptr(),
tensor->weights_data,
tensor->num_weights * equivalent_dtype.value().size());
return {buffer, equivalent_dtype.value()};
}
// ...
}
```
PoC
```bash
# Install MLX
pip install mlx
python3 -c "import mlx.core as mx; mx.load('exploit.gguf', format='gguf')"
```
Download the poc file [there](https://drive.google.com/file/d/1t9Z2RJGn-oHmluKWebU077UWSMGXeuVp/view?usp=sharing), or let me know how I can send it to you.
AddressSanitizer Output (with instrumented build):
```
AddressSanitizer:DEADLYSIGNAL
=================================================================
==5855==ERROR: AddressSanitizer: SEGV on unknown address 0x7fc432f64bc0 (pc 0x7fc430841c12 bp 0x7ffc04847ab0 sp 0x7ffc04847268 T0)
==5855==The signal is caused by a READ memory access.
#0 0x7fc430841c12 /build/glibc-B3wQXB/glibc-2.31/string/../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:312
#1 0x55aac829756b in __asan_memcpy (/home/user1/mlx/fuzz/load_gguf/fuzz_load_gguf+0x9ef56b) (BuildId: 57467f1ce96052757daeef4b04739be7f23c5f1f)
#2 0x55aacaa6e8dc in mlx::core::extract_tensor_data(gguf_tensor*) /home/user1/mlx/mlx/io/gguf.cpp:64:5
#3 0x55aacaa773fc in mlx::core::load_arrays[abi:cxx11](gguf_ctx*) /home/user1/mlx/mlx/io/gguf.cpp:226:35
#4 0x55aacaa782a9 in mlx::core::load_gguf(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&, std::variant<std::monostate, mlx::core::Stream, mlx::core::Device>) /home/user1/mlx/mlx/io/gguf.cpp:250:17
#5 0x55aac82dc696 in LLVMFuzzerTestOneInput /home/user1/mlx/fuzz/load_gguf/fuzz_load_gguf.cpp:49:19
#6 0x55aac81e25c6 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) (/home/user1/mlx/fuzz/load_gguf/fuzz_load_gguf+0x93a5c6) (BuildId: 57467f1ce96052757daeef4b04739be7f23c5f1f)
#7 0x55aac81cc738 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) (/home/user1/mlx/fuzz/load_gguf/fuzz_load_gguf+0x924738) (BuildId: 57467f1ce96052757daeef4b04739be7f23c5f1f)
#8 0x55aac81d220a in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) (/home/user1/mlx/fuzz/load_gguf/fuzz_load_gguf+0x92a20a) (BuildId: 57467f1ce96052757daeef4b04739be7f23c5f1f)
#9 0x55aac81fbb82 in main (/home/user1/mlx/fuzz/load_gguf/fuzz_load_gguf+0x953b82) (BuildId: 57467f1ce96052757daeef4b04739be7f23c5f1f)
#10 0x7fc4307aa082 in __libc_start_main /build/glibc-B3wQXB/glibc-2.31/csu/../csu/libc-start.c:308:16
#11 0x55aac81c73ed in _start (/home/user1/mlx/fuzz/load_gguf/fuzz_load_gguf+0x91f3ed) (BuildId: 57467f1ce96052757daeef4b04739be7f23c5f1f)
==5855==Register values:
rax = 0x0000502000000098 rbx = 0xfafafafa0000fa00 rcx = 0x00000a047fff8013 rdx = 0x0000000000000008
rdi = 0x0000502000000098 rsi = 0x00007fc432f64bc0 rbp = 0x00007ffc04847ab0 rsp = 0x00007ffc04847268
r8 = 0x00000a0400000013 r9 = 0x0000000000000000 r10 = 0x00000a0400000013 r11 = 0x0000000000000000
r12 = 0x00000a047fff8010 r13 = 0xffffffffffffffc7 r14 = 0x00007fc42dd00280 r15 = 0x00000ff885ba0050
AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /build/glibc-B3wQXB/glibc-2.31/string/../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:312
==5855==ABORTING
```
Impact
- Attack vector: Malicious GGUF file (model weights, typically from untrusted sources)
- Affects: MLX users on all platforms who call the vulnerable method with unsanitized input.
- Result: Segmentation fault (uncatchable by exception handlers)
