[Bug] Heap-buffer-overflow in wabt::AST::InsertNode within wasm-decompile

Description

We encountered a Heap-buffer-overflow vulnerability in the wasm-decompile tool. The crash occurs in wabt::AST::InsertNode when processing a specific WebAssembly binary.

The AddressSanitizer (ASan) report indicates that the memory being accessed was freed during a std::vector reallocation (_M_realloc_insert). This suggests a Pointer Invalidation issue where a pointer/reference to a vector element is retained and dereferenced after the vector has been resized and its underlying memory freed.

This issue was reproduced in a Release build (with NDEBUG defined), indicating it is a security vulnerability that affects production environments, potentially leading to Denial of Service (DoS) or memory corruption.

Environment

• OS: Linux x86_64
• Complier: Clang
• Build Configuration: Release mode with ASan enabled.
• Build Command：

make clang-release-asan CMAKE_FLAGS="-DCMAKE_BUILD_TYPE=Release -DUSE_ASAN=ON -DCMAKE_CXX_FLAGS_RELEASE=-DNDEBUG"

Vulnerability Details

• Target: wasm-decompile
• Crash Type: Heap-buffer-overflow (CWE-119 / CWE-416)
• Faulting Instruction: READ of size 8
• Location: wabt::AST::InsertNode
• Root Cause Analysis: The stack trace reveals the following sequence：

1. A std::vectorwabt::Node undergoes reallocation (expansion) via std::vector::_M_realloc_insert.
2. The vector frees its old memory buffer (operator delete is called).
3. wabt::AST::InsertNode subsequently attempts to read from a memory address located in that old, freed buffer.
4. This implies that InsertNode is using a stale pointer or reference to a node that became invalid when the vector resized.

Reproduce

./wasm-decompile ./repro

Download Link: repro

ASAN report

==65981==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x510000000da0 at pc 0x557e6304794a bp 0x7ffc049d18d0 sp 0x7ffc049d18c8
READ of size 8 at 0x510000000da0 thread T0
    #0 0x557e63047949 in wabt::AST::InsertNode(wabt::NodeType, wabt::ExprType, wabt::Expr const*, unsigned int) (/src/repro/wabt/bin/wasm-decompile+0x1c0949) (BuildId: b44cadef6a2094e740cb6ce71ee9a45cfac22974)
    #1 0x557e6303fc7a in wabt::AST::Construct(wabt::intrusive_list<wabt::Expr> const&, unsigned int, unsigned int, bool) (/src/repro/wabt/bin/wasm-decompile+0x1b8c7a) (BuildId: b44cadef6a2094e740cb6ce71ee9a45cfac22974)
    #2 0x557e63047141 in wabt::AST::Construct(wabt::Expr const&) (/src/repro/wabt/bin/wasm-decompile+0x1c0141) (BuildId: b44cadef6a2094e740cb6ce71ee9a45cfac22974)
    #3 0x557e6303e83a in wabt::AST::Construct(wabt::intrusive_list<wabt::Expr> const&, unsigned int, unsigned int, bool) (/src/repro/wabt/bin/wasm-decompile+0x1b783a) (BuildId: b44cadef6a2094e740cb6ce71ee9a45cfac22974)
    #4 0x557e630394f1 in wabt::Decompiler::Decompile[abi:cxx11]() (/src/repro/wabt/bin/wasm-decompile+0x1b24f1) (BuildId: b44cadef6a2094e740cb6ce71ee9a45cfac22974)
    #5 0x557e630372a6 in wabt::Decompile[abi:cxx11](wabt::Module const&, wabt::DecompileOptions const&) (/src/repro/wabt/bin/wasm-decompile+0x1b02a6) (BuildId: b44cadef6a2094e740cb6ce71ee9a45cfac22974)
    #6 0x557e62fd3941 in ProgramMain(int, char**) (/src/repro/wabt/bin/wasm-decompile+0x14c941) (BuildId: b44cadef6a2094e740cb6ce71ee9a45cfac22974)
    #7 0x7f3decb4e1c9  (/lib/x86_64-linux-gnu/libc.so.6+0x2a1c9) (BuildId: 274eec488d230825a136fa9c4d85370fed7a0a5e)
    #8 0x7f3decb4e28a in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2a28a) (BuildId: 274eec488d230825a136fa9c4d85370fed7a0a5e)
    #9 0x557e62ef7584 in _start (/src/repro/wabt/bin/wasm-decompile+0x70584) (BuildId: b44cadef6a2094e740cb6ce71ee9a45cfac22974)

0x510000000da0 is located 2976 bytes after 192-byte region [0x510000000140,0x510000000200)
freed by thread T0 here:
    #0 0x557e62fd1271 in operator delete(void*) (/src/repro/wabt/bin/wasm-decompile+0x14a271) (BuildId: b44cadef6a2094e740cb6ce71ee9a45cfac22974)
    #1 0x557e6304b23f in void std::vector<wabt::Node, std::allocator<wabt::Node>>::_M_realloc_insert<wabt::Node>(__gnu_cxx::__normal_iterator<wabt::Node*, std::vector<wabt::Node, std::allocator<wabt::Node>>>, wabt::Node&&) (/src/repro/wabt/bin/wasm-decompile+0x1c423f) (BuildId: b44cadef6a2094e740cb6ce71ee9a45cfac22974)

previously allocated by thread T0 here:
    #0 0x557e62fd09f1 in operator new(unsigned long) (/src/repro/wabt/bin/wasm-decompile+0x1499f1) (BuildId: b44cadef6a2094e740cb6ce71ee9a45cfac22974)
    #1 0x557e6304acfa in void std::vector<wabt::Node, std::allocator<wabt::Node>>::_M_realloc_insert<wabt::Node>(__gnu_cxx::__normal_iterator<wabt::Node*, std::vector<wabt::Node, std::allocator<wabt::Node>>>, wabt::Node&&) (/src/repro/wabt/bin/wasm-decompile+0x1c3cfa) (BuildId: b44cadef6a2094e740cb6ce71ee9a45cfac22974)

SUMMARY: AddressSanitizer: heap-buffer-overflow (/src/repro/wabt/bin/wasm-decompile+0x1c0949) (BuildId: b44cadef6a2094e740cb6ce71ee9a45cfac22974) in wabt::AST::InsertNode(wabt::NodeType, wabt::ExprType, wabt::Expr const*, unsigned int)
Shadow bytes around the buggy address:
  0x510000000b00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x510000000b80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x510000000c00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x510000000c80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x510000000d00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x510000000d80: fa fa fa fa[fa]fa fa fa fa fa fa fa fa fa fa fa
  0x510000000e00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x510000000e80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x510000000f00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x510000000f80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x510000001000: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==65981==ABORTING

Start with the wasm-decompile entry point and wabt::AST::InsertNode, then reproduce the report using the provided ./wasm-decompile ./repro command and the clang-release-asan build. Trace the reported std::vector reallocation and verify that the supplied repro no longer triggers the ASan heap-buffer-overflow.