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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

7.7 · 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 · score source

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

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…

Published by the source

27 Mar 2026, 22:22 UTC

Last modified by the source

27 Mar 2026, 22:22 UTC

Source last checked

26 Oct 2026, 17:04 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-mvm6-f9r3-fgfx

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# Patch Next advisory brief: GHSA-mvm6-f9r3-fgfx

Advisory: AWS SDK for .NET: Improper escaping of special characters in CloudFront policy document construction
IDs: GHSA-mvm6-f9r3-fgfx
Record: https://patchnext.com/advisories/ghsa-mvm6-f9r3-fgfx (revision 1, source checked 26 Oct 2026, 17:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: awssdk.cloudfront 3.7.510.7; awssdk.extensions.cloudfront.signers 4.0.0.26. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet awssdk.cloudfront: affected < 3.7.510.7; fixed in 3.7.510.7
- NuGet awssdk.extensions.cloudfront.signers: affected >= 4.0.0.0, < 4.0.0.26; fixed in 4.0.0.26

## Suggested inspection (read-only)
- NuGet awssdk.cloudfront: check the installed version with your package manager.
- NuGet awssdk.extensions.cloudfront.signers: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on awssdk.cloudfront, awssdk.extensions.cloudfront.signers.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-mvm6-f9r3-fgfx (GitHub-reviewed advisory GHSA-mvm6-f9r3-fgfx lists affected ranges: NuGet awssdk.cloudfront >=0 =4.0.0.0 <4.0.0.26)

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