CVE-2025-3857 — Amazon.IonDotnet
Fix: amazon-ion/ion-dotnet@34a4f52CVE-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
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
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
Amazon.IonDotnetReal-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
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Amazon.IonDotnet | all versions | 1.3.1dotnet add package Amazon.IonDotnet --version 1.3.1 |
Detection & mitigation playbook
Open-source dependencyDetect
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
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-3857 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-3857. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-3857 in your dependencies?
O3 Security finds CVE-2025-3857 across NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.