CVE-2023-45814 (published 2023-10-18T22:15Z)

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.

CVSS v3 base score: 5.3, MEDIUM (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N)

Weakness information:
cwe_id: CWE-772
cwe_name: Missing Release of Resource after Effective Lifetime
description: The product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed.
extended_description: When a resource is not released after use, it can allow attackers to cause a denial of service by causing the allocation of resources without triggering their release. Frequently-affected resources include memory, CPU, disk space, power or battery, etc.
         

Fix information:
repo_url: https://github.com/LittleBigRefresh/Bunkum
commit_details: repo_url: https://github.com/LittleBigRefresh/Bunkum
author: jvyden
author_date: 2023-10-18 15:56:15-04:00
msg: Prevent IToken use-after-free in AuthenticationService
repository: repo_url: https://github.com/LittleBigRefresh/Bunkum
repo_name: PlanetBunkum/Bunkum
description: A free and open-source protocol-agnostic request server built with flexibility yet ease of use in mind.
repo_language: C#
owner: LittleBigRefresh
file_changes: filename: AuthenticationService.cs
change_type: ModificationType.MODIFY
diff: @@ -68,9 +68,14 @@ public class AuthenticationService : Service
             IToken<IUser>? token = this.AuthenticateToken(context, database);
             if (token != null) return token.User;
         }
+        
+        return null;
+    }
 
+    /// <inheritdoc />
+    public override void AfterRequestHandled(ListenerContext context, Response response, MethodInfo method, Lazy<IDatabaseContext> database)
+    {
         this._tokenCache.Value = null;
-        return null;
     }
 
     public IToken<IUser>? AuthenticateToken(ListenerContext context, Lazy<IDatabaseContext> database, bool remove = false)

programming_language: C#