How severe is CVE-2025-3857?

No CVSS score has been assigned to CVE-2025-3857 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-3857?

CVE-2025-3857 affects the following packages: Amazon.IonDotnet (NuGet). Ecosystems affected: NuGet.

How do I fix CVE-2025-3857?

Update Amazon.IonDotnet to 1.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-3857 is resolved across your whole dependency graph.

How do I detect CVE-2025-3857 in my NuGet dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Amazon.IonDotnet, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-3857 if there is no patch (or I can't update yet)?

Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Is CVE-2025-3857 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-3857 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-3857?

CVE-2025-3857 has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 50th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-3857?

CVE-2025-3857 is classified as Deserialization of Untrusted Data (CWE-502), CWE-835 (CWE-835). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2025-3857 published, and has it been updated?

CVE-2025-3857 was published on April 21, 2025 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

.NET NuGet

Not in CISA KEV

CVE-2025-3857 — Amazon.IonDotnet

Fix: amazon-ion/ion-dotnet@34a4f52

CVE-2025-3857 is a Deserialization of Untrusted Data vulnerability in Amazon.IonDotnet. A fix is available for Amazon.IonDotnet — see the affected versions and patch details below.

Infinite loop condition in Amazon.IonDotnet

Also known asGHSA-gm2p-wf5c-w3pj

Published

Apr 21, 2025

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-3857.

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs50th percentile — riskier than 50% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

.NETAmazon.IonDotnet

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

Description

Summary

Amazon.IonDotnet (ion-dotnet) is a .NET library with an implementation of the Ion data serialization format.

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. 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 or directly via email to [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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
.NETNuGet	`Amazon.IonDotnet`	all versions	1.3.1`dotnet add package Amazon.IonDotnet --version 1.3.1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Amazon.IonDotnet, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update Amazon.IonDotnet to 1.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-3857 is resolved across your whole dependency graph.
Workarounds
Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Frequently Asked Questions

## 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 m

O3 Security · Impact-Aware SCA

Is CVE-2025-3857 in your dependencies?

Find it across NuGet, including transitive dependencies.

Scan my dependencies How O3 SCA works