GHSA-MVM6-F9R3-FGFX

GHSA-MVM6-F9R3-FGFX is a high-severity improper input validation vulnerability in AWSSDK.CloudFront (nuget), affecting versions < 3.7.510.7. It is fixed in 3.7.510.7, 4.0.0.26.

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Summary

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

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.

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

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.

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.

The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.

Affected versions

AWSSDK.CloudFront (< 3.7.510.7) AWSSDK.Extensions.CloudFront.Signers (>= 4.0.0.0, < 4.0.0.26)

Security releases

AWSSDK.CloudFront → 3.7.510.7 (nuget) AWSSDK.Extensions.CloudFront.Signers → 4.0.0.26 (nuget)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

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.

Frequently Asked Questions

  1. What is GHSA-MVM6-F9R3-FGFX? GHSA-MVM6-F9R3-FGFX is a high-severity improper input validation vulnerability in AWSSDK.CloudFront (nuget), affecting versions < 3.7.510.7. It is fixed in 3.7.510.7, 4.0.0.26. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
  2. Which packages are affected by GHSA-MVM6-F9R3-FGFX?
    • AWSSDK.CloudFront (nuget) (versions < 3.7.510.7)
    • AWSSDK.Extensions.CloudFront.Signers (nuget) (versions >= 4.0.0.0, < 4.0.0.26)
  3. Is there a fix for GHSA-MVM6-F9R3-FGFX? Yes. GHSA-MVM6-F9R3-FGFX is fixed in 3.7.510.7, 4.0.0.26. Upgrade to this version or later.
  4. Is GHSA-MVM6-F9R3-FGFX exploitable, and should I be worried? Whether GHSA-MVM6-F9R3-FGFX is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
  5. What actually determines whether GHSA-MVM6-F9R3-FGFX is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
  6. How do I fix GHSA-MVM6-F9R3-FGFX?
    • Upgrade AWSSDK.CloudFront to 3.7.510.7 or later
    • Upgrade AWSSDK.Extensions.CloudFront.Signers to 4.0.0.26 or later

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