CVE-2023-45814 Tokens cached in the AuthenticationService are susceptible to reuse in Bunkum
Cached authentication tokens persist beyond request lifetime, allowing potential reuse of expired or detached tokens in Bunkum game server libraries.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-45814?
CVE-2023-45814 is a medium-severity use after free vulnerability in LittleBigRefresh Bunkum, published on 18 Oct 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Bunkum is an open-source protocol-agnostic request server for custom game servers. First, a little bit of background. So, in the beginning, Bunkum's `AuthenticationService` only supported injecting `IUser`s. However, as Refresh and SoundShapesServer implemented permissions systems support for injecting `IToken`s into endpoints was added. All was well until 4.0. Bunkum 4.0 then changed to enforce relations between `IToken`s and `IUser`s. This wasn't implemented in a very good way in the `AuthenticationService`, and ended up breaking caching in such a way that cached tokens would persist after the lifetime of the request - since we tried to cache both tokens and users. From that point until now, from what I understand, Bunkum was attempting to use that cached token at the start of the next request once cached. Naturally, when that token expired, downstream projects like Refresh would remove the object from Realm - and cause the object in the cache to be in a detached state, causing an exception from invalid use of `IToken.User`. So in other words, a use-after-free since Realm can't manage the lifetime of the cached token. Security-wise, the scope is fairly limited, can only be pulled off on a couple endpoints given a few conditions, and you can't guarantee which token you're going to get. Also, the token *would* get invalidated properly if the endpoint had either a `IToken` usage or a `IUser` usage. The fix is to just wipe the token cache after the request was handled, which is now in `4.2.1`. Users are advised to upgrade. There are no known workarounds for this vulnerability.
Weakness: CWE-772
Which versions are affected by CVE-2023-45814?
2 open source packages ship an affected version, including Bunkum. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
Bunkum NuGet | From 4.0.0 | 4.2.1 |
Bunkum NuGet | From 4.0.0 | 4.2.1 |
Products include Littlebigfresh Bunkum.
How do I fix CVE-2023-45814?
Upgrade Bunkum to 4.2.1 or later.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2023-45814 being exploited?
There is no known exploitation of CVE-2023-45814 in the wild and no public exploit code.
Sources
Also known as GHSA-jrf2-h5j6-3rrq.