CVE-2025-62609: MLX has Wild Pointer Dereference in load_gguf()

Summary

Segmentation fault in mlx::core::loadgguf() 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 extracttensordata() at lines 59-79 - Vulnerable memcpy at lines 64-67 - Called from loadarrays() at line 177

The Bug: cpp std::tuple<allocator::Buffer, Dtype> extracttensordata(gguftensor tensor) { std::optional<Dtype> equivalentdtype = gguftypetodtype(tensor->type); if (equivalentdtype.hasvalue()) { allocator::Buffer buffer = allocator::malloc(tensor->bsize); memcpy( buffer.rawptr(), tensor->weightsdata, // untrusted pointer from gguflib tensor->numweights equivalentdtype.value().size()); return {buffer, equivalentdtype.value()}; } // ... }

Possible Fix

cpp std::tuple<allocator::Buffer, Dtype> extracttensordata(gguftensor tensor) { std::optional<Dtype> equivalentdtype = gguftypetodtype(tensor->type); if (equivalentdtype.hasvalue()) { // FIX: Validate pointer if (!tensor->weightsdata) { throw std::runtimeerror("[loadgguf] NULL tensor data pointer"); }

allocator::Buffer buffer = allocator::malloc(tensor->bsize); memcpy( buffer.rawptr(), tensor->weightsdata, tensor->numweights equivalentdtype.value().size()); return {buffer, equivalentdtype.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/x8664/multiarch/memmove-vec-unaligned-erms.S:312 #1 0x55aac829756b in asanmemcpy (/home/user1/mlx/fuzz/loadgguf/fuzzloadgguf+0x9ef56b) (BuildId: 57467f1ce96052757daeef4b04739be7f23c5f1f) #2 0x55aacaa6e8dc in mlx::core::extracttensordata(gguftensor) /home/user1/mlx/mlx/io/gguf.cpp:64:5 #3 0x55aacaa773fc in mlx::core::loadarraysabi:cxx11 /home/user1/mlx/mlx/io/gguf.cpp:226:35 #4 0x55aacaa782a9 in mlx::core::loadgguf(std::cxx11::basicstring<char, std::chartraits<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/loadgguf/fuzzloadgguf.cpp:49:19 #6 0x55aac81e25c6 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const, unsigned long) (/home/user1/mlx/fuzz/loadgguf/fuzzloadgguf+0x93a5c6) (BuildId: 57467f1ce96052757daeef4b04739be7f23c5f1f) #7 0x55aac81cc738 in fuzzer::RunOneTest(fuzzer::Fuzzer, char const, unsigned long) (/home/user1/mlx/fuzz/loadgguf/fuzzloadgguf+0x924738) (BuildId: 57467f1ce96052757daeef4b04739be7f23c5f1f) #8 0x55aac81d220a in fuzzer::FuzzerDriver(int, char, int ()(unsigned char const, unsigned long)) (/home/user1/mlx/fuzz/loadgguf/fuzzloadgguf+0x92a20a) (BuildId: 57467f1ce96052757daeef4b04739be7f23c5f1f) #9 0x55aac81fbb82 in main (/home/user1/mlx/fuzz/loadgguf/fuzzloadgguf+0x953b82) (BuildId: 57467f1ce96052757daeef4b04739be7f23c5f1f) #10 0x7fc4307aa082 in libcstartmain /build/glibc-B3wQXB/glibc-2.31/csu/../csu/libc-start.c:308:16 #11 0x55aac81c73ed in start (/home/user1/mlx/fuzz/loadgguf/fuzzloadgguf+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/x8664/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)