CVE-2025-3857

Description

## Summary [Amazon.IonDotnet (ion-dotnet)](https://github.com/amazon-ion/ion-dotnet) is a .NET library with an implementation of the [Ion data serialization format](https://amazon-ion.github.io/ion-docs/). An issue exists in Amazon.IonDotnet and the RawBinaryReader class where, under certain conditions, an actor could trigger an infinite loop condition. ## Impact When reading binary Ion data through Amazon.IonDotnet using the RawBinaryReader class, Amazon.IonDotnet does not check the number of bytes read from the underlying stream while deserializing the binary format. If the Ion data is malformed or truncated, this triggers an infinite loop condition that could potentially result in a denial of service. **Impacted versions: <=1.3.0** ## Patches This issue has been addressed in Amazon.IonDotnet version [1.3.1](https://github.com/amazon-ion/ion-dotnet/releases/tag/v1.3.1). We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes. ## Workarounds There are no workarounds. Upgrade to version 1.3.1. ## References If you have any questions or comments about this advisory, contact AWS/Amazon Security via our [vulnerability reporting page](https://aws.amazon.com/security/vulnerability-reporting) or directly via email to [[email protected]](mailto:[email protected]). Please do not create a public GitHub issue. ## Credit We would like to thank Josh Coleman from Symbotic for collaborating on this issue through the coordinated vulnerability disclosure process.

How to fix CVE-2025-3857

To remediate CVE-2025-3857, upgrade the affected package to a fixed version below.

• —upgrade to 1.3.1 or later

Is CVE-2025-3857 being exploited?

Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.

Affected packages (1)

• from 0, < 1.3.1