GHSA-mvm6-f9r3-fgfx AWS SDK for .NET: Improper escaping of special characters in CloudFront policy document construction

Q: Which versions are affected by GHSA-mvm6-f9r3-fgfx?

4 open source packages ship an affected version, including AWSSDK.CloudFront and AWSSDK.Extensions.CloudFront.Signers.

Q: Is GHSA-mvm6-f9r3-fgfx being exploited?

There is no known exploitation of GHSA-mvm6-f9r3-fgfx in the wild and no public exploit code.

Q: How do I fix GHSA-mvm6-f9r3-fgfx?

Upgrade AWSSDK.CloudFront to 3.7.510.7 or later.

Not scored Published 27 Mar 2026

Improper escaping in CloudFront signing utilities may allow bypassing intended access restrictions if input is unsanitized.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is GHSA-mvm6-f9r3-fgfx?

GHSA-mvm6-f9r3-fgfx is a vulnerability in AWSSDK.CloudFront, published on 27 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Which versions are affected by GHSA-mvm6-f9r3-fgfx?