CVE-2024-48924 MessagePack allows untrusted data to lead to DoS attack due to hash collisions and stack overflow

What is CVE-2024-48924?

CVE-2024-48924 is a high-severity denial of service vulnerability in MessagePack-CSharp, published on 17 Oct 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

### 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<T>` method to provide a collision-resistant hash function of your own and avoid calling `base.GetHashCollisionResistantEqualityComparer<T>()`. 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])

Weakness: CWE-328

Which versions are affected by CVE-2024-48924?

4 open source packages ship an affected version, including MessagePack.

How do I fix CVE-2024-48924?

Upgrade MessagePack to a fixed version for your release line: 2.5.187 or 3.0.214-rc.1.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2024-48924 being exploited?

There is no known exploitation of CVE-2024-48924 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ECHO-d0e4-8926-1c6a, GHSA-4qm4-8hg2-g2xm.