The dec2lha library is the library responsible for decompressing LZH and LHA archives. The CSymLHA::get_header() routine has a trivial stack buffer overflow. .text:00023D91 31 C0 xor eax, eax ... .text:00023DAE 8D 95 E4 FB FF+ lea edx, [ebp+var_41C] .text:00023DB4 89 D7 mov edi, edx .text:00023DC7 66 B9 00 01 mov cx, 100h .text:00023DCB F3 AB rep stosd We can see from this initialization that var_141C is a 1024 byte stack buffer, because 0x100 * sizeof(dword) = 1024. But later on in this routine: .text:0002442C 88 0C 10 mov [eax+edx], cl ; eax = &var_41C edx=index .text:0002442F 83 C2 01 add edx, 1 ; edx++ ... .text:00024408 81 FA 00 10 00+ cmp edx, 1000h ; if (index > 4096) ... .text:0002440E 0F 84 E9 02 00+ jz loc_246FD ; oob The index is checked to see if it's > 4096 bytes, this is incorrect. This is most likely a simple programmers error, bounds checking with the wrong size. This code is typically run with SYSTEM/root privileges, I'm using Symantec Scan Engine on Linux to reproduce this issue, but all platforms and products using this code (e.g. Symantec Mail Security) are likely affected. #0 0xf5606d95 in CSymLHA::get_header(SymLHA::_S_LzHeader*) () from libdec2lha.so #1 0xf5607af4 in CSymLHA::GetEntry(SymLHA::_S_LzHeader*) () from libdec2lha.so #2 0xf55e83d5 in CLHAEngine::ProcessChildren(IDecomposerEx*, IDecContainerObjectEx*, IDecEventSink*, unsigned short*, char*, CSymLHA*) () from libdec2lha.so #3 0xf55e8a8f in CLHAEngine::Process(IDecomposerEx*, IDecContainerObjectEx*, IDecEventSink*, unsigned short*, char*, bool*, bool*) () from libdec2lha.so #4 0xf5c137b5 in CDecomposer::DecProcess(IDecObject*, IDecEventSink*, IDecIOCB*, unsigned short*, char*) () #5 0xf5c143cb in CDecomposer::Process(IDecObject*, IDecEventSink*, IDecIOCB*, unsigned short*, char*) () (gdb) c Program received signal SIGSEGV, Segmentation fault. 0x41414141 in ?? () Because Symantec do not use -fstack-protector on Linux, exploitation is remarkably trivial. Exploitation is likely still possible on Windows, but may be more difficult as they do use /GS on that platform. This issue is remotely exploitable just by receiving an email, visiting a website, and so on. More: https://bugs.chromium.org/p/project-zero/issues/detail?id=814