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GHSA-mvm6-f9r3-fgfx — AWSSDK.CloudFront

GHSA-mvm6-f9r3-fgfx is a security vulnerability in AWSSDK.CloudFront. A fix is available for AWSSDK.CloudFront — see the affected versions and patch details below.

AWS SDK for .NET: Improper escaping of special characters in CloudFront policy document construction

Published
Mar 27, 2026
Updated
Mar 27, 2026
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Mar 27, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

2 pkgs affected
.NETAWSSDK.CloudFront.NETAWSSDK.Extensions.CloudFront.Signers

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

This notification is related to the CloudFront signing utilities in the AWS SDK for .NET, which are used to generate Amazon CloudFront signed URLs and signed cookies. A defense-in-depth enhancement has been implemented to improve handling of special characters, such as double quotes and backslashes, in input values.

Impact

The CloudFront signing utilities build policy documents that define access restrictions for signed URLs and cookies. If an application passes unsanitized input containing special characters to these utilities, the resulting policy document may not reflect the application's intended access restrictions. While the SDK was functioning safely within the requirements of the shared responsibility model, additional safeguards have been added to support secure customer implementations. Applications that already follow AWS security best practices for input validation are not impacted.

Impacted versions:

  • AWS SDK for .NET V3 (AWSSDK.CloudFront): < 3.7.510.7
  • AWS SDK for .NET V4 (AWSSDK.Extensions.CloudFront.Signers): 4.0.0.0 - 4.0.0.25

Patches

On February 25th, 2026, an enhancement was made to the AWS SDK for .NET CloudFront signing utilities. The enhancement ensures that special characters in input values are correctly handled. We recommend upgrading to the latest version.

Workarounds

No workarounds are needed, but customers should ensure that your application is following security best practices:

  • Implement proper input validation in your application code before passing values to CloudFront signing utilities
  • Update to the latest AWS SDK release on a regular basis
  • Follow AWS security best practices for SDK configuration

References

If there are any questions or comments about this advisory, contact AWS Security via our vulnerability reporting page or directly via email to [email protected]. Please do not create a public GitHub issue.

Acknowledgement

AWS SDK for .NET thanks the Amazon Inspector Security Research team for identifying this issue and working through the coordinated process together.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
.NETNuGetAWSSDK.CloudFrontall versions3.7.510.7dotnet add package AWSSDK.CloudFront --version 3.7.510.7
.NETNuGetAWSSDK.Extensions.CloudFront.Signers≥ 4.0.0.0&&< 4.0.0.264.0.0.26dotnet add package AWSSDK.Extensions.CloudFront.Signers --version 4.0.0.26

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update AWSSDK.CloudFront to 3.7.510.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mvm6-f9r3-fgfx is resolved across your whole dependency graph.

  3. 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.

  4. How O3 protects you

    O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-mvm6-f9r3-fgfx can be triaged on real exposure rather than presence alone.

Tailored to GHSA-mvm6-f9r3-fgfx. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary This notification is related to the CloudFront signing utilities in the AWS SDK for .NET, which are used to generate Amazon CloudFront signed URLs and signed cookies. A defense-in-depth enhancement has been implemented to improve handling of special characters, such as double quotes and backslashes, in input values. ### Impact The CloudFront signing utilities build policy documents that define access restrictions for signed URLs and cookies. If an application passes unsanitized input containing special characters to these utilities, the resulting policy document may not reflect
O3 Security · Impact-Aware SCA

Is GHSA-mvm6-f9r3-fgfx in your dependencies?

O3 Security finds GHSA-mvm6-f9r3-fgfx across NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

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GHSA-mvm6-f9r3-fgfx: AWSSDK.CloudFront | O3 Security