Deno is a JavaScript, TypeScript, and WebAssembly runtime. Starting in version 1.36.2 and prior to version 1.40.3, use of inherently unsafe `*const c_void` and `ExternalPointer` leads to use-after-free access of the underlying structure, resulting in arbitrary code execution. Use of inherently unsafe `*const c_void` and `ExternalPointer` leads to use-after-free access of the underlying structure, which is exploitable by an attacker controlling the code executed inside a Deno runtime to obtain arbitrary code execution on the host machine regardless of permissions. This bug is known to be exploitable for both `*const c_void` and `ExternalPointer` implementations. Version 1.40.3 fixes this issue.
Affected: crates.io: deno
### Summary
Use of inherently unsafe `*const c_void` and `ExternalPointer` leads to use-after-free access of the underlying structure, resulting in arbitrary code execution.
### Details
`*const c_void` and `ExternalPointer` (defined via `external!()` macros) types are used to represent `v8::External` wrapping arbitrary `void*` with an external lifetime. This is inherently unsafe as we are effectively eliding all Rust lifetime safety guarantees.
`*const c_void` is trivially unsafe. `ExternalPointer` attempts to resolve this issue by wrapping the underlying pointer with a `usize`d marker ([`ExternalWithMarker<T>`](https://github.com/denoland/deno_core/blob/a2838062a8f51926140a48a8aa926330c6f9070c/core/external.rs#L49)).
However, the marker [relies on the randomness of PIE address (binary base address)](https://github.com/denoland/deno_core/blob/a2838062a8f51926140a48a8aa926330c6f9070c/core/external.rs#L10) which is still trivially exploitable for a non-PIE binary. It is also equally exploitable on a PIE binary when an attacker is able to derandomize the PIE address. This is problematic as it escalates an information leak of the PIE address into an exploitable vulnerability.
Note that an attacker able to control code executed inside the Deno runtime is very likely to be able to bypass ASLR with any means necessary (e.g. by chaining another vulnerability, or by using other granted permissions such as `--allow-read` to read `/proc/self/maps`).
### PoC
For simplicity, we…