Thanks! These claims are really interesting. - WASM has no ASLR. If I understand correctly, the attack vector here is that if a buffer overrun lets you modify

Thanks! These claims are really interesting. - WASM has no ASLR. If I understand correctly, the attack vector here is that if a buffer overrun lets you modify a function pointer, you could replace that function pointer with another pointer to have the program execute different code. As you say, this is hard in native linux programs because of ASLR. You need a pointer to some code thats loaded in memory and you need to know where it is. In wasm, the "pointer" isn't a pointer at all. indirect_call takes an index into the jump table. Yes, this makes it easier to find other valid function pointers. But wasm also has some advantages here. Unlike in native code, you can't "call" arbitrary locations in memory. And indirect_call is also runtime typechecked. So you can't call functions with an unexpected type signature. Also (I think) the jump table itself can't be edited by the running wasm module. So there's no way to inject code into the module and run it. You only have access to call the already-loaded functions that are in the jump table. And amongst those, you can only substitute one with a matching type signature. I agree - ASLR could help here. But it still doesn't sound super easy to exploit. That said, it might be much easier to exploit this with wasi when the function table is filled with unix syscalls. Docs: https://developer.mozilla.org/en-US/docs/WebAssembly/Understanding_the_text_format#webassembly_tables https://developer.mozilla.org/en-US/docs/WebAssembly/Underst... - WASM allows writing to 0x0. You're probably right about this. To be clear, it means if pointers are set to 0 then dereferenced, the program might continue before crashing. And the memory around 0 may be overwritten by an attacker. How bad this is in practice depends on the prevelance of use-after-free bugs (common in C / C++) and what ends up near 0 in memory. In rust, these sort of software bugs seem incredibly rare. And I wouldn't be surprised if wasm compilers for C/C++ start making a memory deadzone here - if they aren't doing that already. - wasm can easily overflow buffers Sure, but so can native C code. And unlike native code, wasm can't overflow buffers outside of the data section. So you can't overwrite methods or modify the memory of any other loaded modules. So on net, wasm is still marginally safer than native code here. If you're worried about buffer overflows, use a safer language. - wasm doesn't have the concept of read-only memory Interesting! I can see this definitely being useful for system libraries like mmap. This would definitely be nice to have, and it looks like the wasm authors agree with you. https://github.com/WebAssembly/multi-memory/issues/15 https://github.com/WebAssembly/multi-memory/issues/15