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.
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.
AWSSDK.CloudFront): < 3.7.510.7AWSSDK.Extensions.CloudFront.Signers): 4.0.0.0 - 4.0.0.25On 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.
No workarounds are needed, but customers should ensure that your application is following security best practices:
If there are any questions or comments about this advisory, contact AWS Security via our vulnerability reporting page or directly via email to aws-security@amazon.com. Please...
3.7.510.74.0.0.26Exploitability
AV:NAC:LAT:NPR:NUI:NVulnerable System
VC:NVI:LVA:NSubsequent System
SC:HSI:NSA:N7.7/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