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🛡️ GHSA-mvm6-f9r3-fgfx — awssdk.cloudfront

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-116 OSV
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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

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](https://aws.amazon.com/security/vulnerability-reporting) or directly via email to [aws-security@amazon.com](mailto:aws-security@amazon.com). 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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. Rated impact: confidentiality none, integrity low, availability none.

Weakness class

GHSA-mvm6-f9r3-fgfx is classified as CWE-116: Improper Encoding or Escaping of Output. Output is emitted without encoding it for the context it lands in, so data is interpreted as markup or code.

Affected software

GHSA-mvm6-f9r3-fgfx is recorded against 2 packages.

  • awssdk.cloudfront (fixed in 3.7.510.7)
  • awssdk.extensions.cloudfront.signers (from 4.0.0.0 up to 4.0.0.26)

Timeline and source

Published on 27 March 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

github.com (Web)
github.com (Package)

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:H/SI:N/SA:N
CWE CWE-116
Public Exploit ✅ No
Source OSV
Published 2026-03-27
Updated 2026-08-20
Modified 2026-03-27
Fix URL N/A

Affected Packages

Software From version Fixed in
awssdk.cloudfront — 3.7.510.7
awssdk.extensions.cloudfront.signers 4.0.0.0 4.0.0.26

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