CVE-2023-45814

Bunkum tokens cached in the AuthenticationService are susceptible to a use-after-free

First, a little bit of background. So, in the beginning, Bunkum's AuthenticationService only supported injecting IUsers. However, as Refresh and SoundShapesServer implemented permissions systems support for injecting ITokens into endpoints was added. All was well until 4.0.

Bunkum 4.0 then changed to enforce relations between ITokens and IUsers. 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. User interaction is required as authenticated requests must be performed.

CVE-2023-45814 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.2.1); upgrading removes the vulnerable code path.

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The fix is to just wipe the token cache after the request was handled, which is now in 4.2.1. I'd recommend that you update. Unfortunately, there are no real workarounds for other versions in the 4.X.X range.

1. What is CVE-2023-45814? CVE-2023-45814 is a medium-severity security vulnerability in Bunkum (nuget), affecting versions >= 4.0.0, < 4.2.1. It is fixed in 4.2.1.
2. How severe is CVE-2023-45814? CVE-2023-45814 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of Bunkum are affected by CVE-2023-45814? Bunkum (nuget) versions >= 4.0.0, < 4.2.1 is affected.
4. Is there a fix for CVE-2023-45814? Yes. CVE-2023-45814 is fixed in 4.2.1. Upgrade to this version or later.
5. Is CVE-2023-45814 exploitable, and should I be worried? Whether CVE-2023-45814 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-45814 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-45814? Upgrade Bunkum to 4.2.1 or later.