# GHSA-mvm6-f9r3-fgfx: AWS SDK for .NET: Improper escaping of special characters in CloudFront policy document construction > Improper escaping in CloudFront signing utilities may allow bypassing intended access restrictions if input is unsanitized. - **Severity:** Not scored - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 27 Mar 2026 ## 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](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. ## 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. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `AWSSDK.CloudFront` | NuGet | All versions | 3.7.510.7 | | `AWSSDK.CloudFront` | NuGet | All versions | 3.7.510.7 | | `AWSSDK.Extensions.CloudFront.Signers` | NuGet | From 4.0.0.0 | 4.0.0.26 | | `AWSSDK.Extensions.CloudFront.Signers` | NuGet | From 4.0.0.0 | 4.0.0.26 | ## How do I fix GHSA-mvm6-f9r3-fgfx? Upgrade AWSSDK.CloudFront to 3.7.510.7 or later. ## 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. ## Fix prompt for AI coding agents ```text Check this codebase for GHSA-mvm6-f9r3-fgfx and fix it if it is affected. What it is: 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. Exploitation: There is no known exploitation of GHSA-mvm6-f9r3-fgfx in the wild and no public exploit code. Affected packages and fixed versions: - AWSSDK.CloudFront (NuGet): affected all versions; fixed in 3.7.510.7 - AWSSDK.CloudFront (NuGet): affected all versions; fixed in 3.7.510.7 - AWSSDK.Extensions.CloudFront.Signers (NuGet): affected from 4.0.0.0; fixed in 4.0.0.26 - AWSSDK.Extensions.CloudFront.Signers (NuGet): affected from 4.0.0.0; fixed in 4.0.0.26 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/GHSA-mvm6-f9r3-fgfx/ (Markdown: https://insights.sbomify.com/GHSA-mvm6-f9r3-fgfx/index.md) ``` ## Sources - OSV: https://osv.dev/vulnerability/GHSA-mvm6-f9r3-fgfx --- From sbomify Insights: https://insights.sbomify.com/GHSA-mvm6-f9r3-fgfx/ Summaries are generated and may contain mistakes; the official description above is the record.