MessagePack-CSharp up to 2.5.186/3.0.213 GetHashCollisionResistantEqualityComparer weak hash

Summaryinfo

A vulnerability labeled as critical has been found in MessagePack-CSharp up to 2.5.186/3.0.213. Affected by this issue is the function GetHashCollisionResistantEqualityComparer. Executing a manipulation can lead to weak hash. The identification of this vulnerability is CVE-2024-48924. The attack may be launched remotely. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as critical was found in MessagePack-CSharp up to 2.5.186/3.0.213. This vulnerability affects the function GetHashCollisionResistantEqualityComparer. The manipulation with an unknown input leads to a weak hash vulnerability. The CWE definition for the vulnerability is CWE-328. The product uses an algorithm that produces a digest (output value) that does not meet security expectations for a hash function that allows an adversary to reasonably determine the original input (preimage attack), find another input that can produce the same hash (2nd preimage attack), or find multiple inputs that evaluate to the same hash (birthday attack). As an impact it is known to affect availability. CVE summarizes:

### Impact When this library is used to deserialize messagepack data from an untrusted source, there is a risk of a denial of service attack by an attacker that sends data contrived to produce hash collisions, leading to large CPU consumption disproportionate to the size of the data being deserialized. This is similar to [a prior advisory](https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-7q36-4xx7-xcxf), which provided an inadequate fix for the hash collision part of the vulnerability. ### Patches The following steps are required to mitigate this risk. 1. Upgrade to a version of the library where a fix is available. 1. Review the steps in [this previous advisory](https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-7q36-4xx7-xcxf) to ensure you have your application configured for untrusted data. ### Workarounds If upgrading MessagePack to a patched version is not an option for you, you may apply a manual workaround as follows: 1. Declare a class that derives from `MessagePackSecurity`. 2. Override the `GetHashCollisionResistantEqualityComparer` method to provide a collision-resistant hash function of your own and avoid calling `base.GetHashCollisionResistantEqualityComparer()`. 3. Configure a `MessagePackSerializerOptions` with an instance of your derived type by calling `WithSecurity` on an existing options object. 4. Use your custom options object for all deserialization operations. This may be by setting the `MessagePackSerializer.DefaultOptions` static property, if you call methods that rely on this default property, and/or by passing in the options object explicitly to any `Deserialize` method. ### References - Learn more about best security practices when reading untrusted data with [MessagePack 1.x](https://github.com/MessagePack-CSharp/MessagePack-CSharp/tree/v1.x#security) or [MessagePack 2.x](https://github.com/MessagePack-CSharp/MessagePack-CSharp#security). - The .NET team's [discussion on hash collision vulnerabilities of their `HashCode` struct](https://github.com/GrabYourPitchforks/runtime/blob/threat_models/docs/design/security/System.HashCode.md). ### For more information If you have any questions or comments about this advisory: * [Start a public discussion](https://github.com/MessagePack-CSharp/MessagePack-CSharp/discussions) * [Email us privately](mailto:[email protected])

The advisory is shared for download at github.com. This vulnerability was named CVE-2024-48924 since 10/10/2024. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1600.001.

Upgrading to version 2.5.187 or 3.0.214-rc.1 eliminates this vulnerability. Applying the patch 8e599af0798b45008f8b293a7f233e4878f11ed5 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Name

• MessagePack-CSharp

Version

• 2.5.186
• 3.0.213

License

• open-source

Website

• Product: https://github.com/MessagePack-CSharp/MessagePack-CSharp/

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