# GHSA-rxhx-9fj6-6h2m: enum_map macro can cause UB when `Enum` trait is incorrectly implemented

> Incorrect manual implementation of the Enum trait in the enum-map crate can lead to uninitialized memory usage and arbitrary code execution.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Not stated
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Feb 2022
- **Also known as:** RUSTSEC-2022-0010

## What is GHSA-rxhx-9fj6-6h2m?

GHSA-rxhx-9fj6-6h2m is a memory corruption vulnerability in enum-map, published on 17 Feb 2022. 

### Official description

Affected versions of this crate did not properly check the length of an enum when using `enum_map!` macro, trusting user-provided length.

When the `LENGTH` in the `Enum` trait does not match the array length in the `EnumArray` trait, this can result in the initialization of the enum map with uninitialized types, which in turn can allow an attacker to execute arbitrary code.

This problem can only occur with a manual implementation of the Enum trait, it will never occur for enums that use `#[derive(Enum)]`.

Example code that triggers this vulnerability looks like this:

```rust
enum E {
    A,
    B,
    C,
}

impl Enum for E {
    const LENGTH: usize = 2;

    fn from_usize(value: usize) -> E {
        match value {
            0 => E::A,
            1 => E::B,
            2 => E::C,
            _ => unimplemented!(),
        }
    }

    fn into_usize(self) -> usize {
        self as usize
    }
}

impl<V> EnumArray<V> for E {
    type Array = [V; 3];
}

let _map: EnumMap<E, String> = enum_map! { _ => "Hello, world!".into() };
```

The flaw was corrected in commit [b824e23](https://gitlab.com/KonradBorowski/enum-map/-/commit/b824e232f2fb47837740070096ac253df8e80dfc) by putting `LENGTH` property on sealed trait for macro to read.

## Which versions are affected by GHSA-rxhx-9fj6-6h2m?

3 open source packages ship an affected version, including enum-map.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `enum-map` | crates.io | From 2.0.0-2 | 2.0.2 |
| `enum-map` | crates.io | From 2.0.0-2 | 2.0.2 |
| `enum-map` | crates.io | From 2.0.0-2 | 2.0.2 |

## How do I fix GHSA-rxhx-9fj6-6h2m?

Upgrade enum-map to 2.0.2 or later.

## Is GHSA-rxhx-9fj6-6h2m being exploited?

There is no known exploitation of GHSA-rxhx-9fj6-6h2m in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-rxhx-9fj6-6h2m and fix it if it is affected.

What it is: GHSA-rxhx-9fj6-6h2m is a memory corruption vulnerability in enum-map, published on 17 Feb 2022. 
Exploitation: There is no known exploitation of GHSA-rxhx-9fj6-6h2m in the wild and no public exploit code.

Affected packages and fixed versions:
- enum-map (crates.io): affected from 2.0.0-2; fixed in 2.0.2
- enum-map (crates.io): affected from 2.0.0-2; fixed in 2.0.2
- enum-map (crates.io): affected from 2.0.0-2; fixed in 2.0.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/GHSA-rxhx-9fj6-6h2m/ (Markdown: https://insights.sbomify.com/GHSA-rxhx-9fj6-6h2m/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-rxhx-9fj6-6h2m

---
From sbomify Insights: https://insights.sbomify.com/GHSA-rxhx-9fj6-6h2m/
Summaries are generated and may contain mistakes; the official description above is the record.