GHSA-j842-xgm4-wf88 MLX has Wild Pointer Dereference in load_gguf()

• PyPI mlx: < 0.29.4 → fixed in 0.29.4

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 extract_tensor_data(gguf_tensor* tensor) { std::optional 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 extract_tensor_data(gguf_tensor* tensor) { std::optional 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, 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_arraysabi:cxx11 /home/user1/mlx/mlx/io/gguf.cpp:226:35 #4 0x55aacaa782a9 in mlx::core::load_gguf(std::__cxx11::basic_string, std::allocator> const&, std::variant) /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) --- Credits: • Markiyan Melnyk (ARIMLABS) • Mykyta Mudryi (ARIMLABS) • Markiyan Chaklosh (ARIMLABS)