CVE-2026-22611: AWS SDK for .NET SSRF Vulnerability

CVE-2026-22611 Overview

AWS SDK for .NET, which enables developers to build scalable solutions with Amazon S3, Amazon DynamoDB, Amazon Glacier, and other AWS services, contains an improper input validation vulnerability affecting versions 4.0.0 to before 4.0.3.3. Customer applications could be configured to improperly route AWS API calls to non-existent or non-AWS hosts due to insufficient validation of the region input field when calling AWS services. An actor with access to the environment in which the SDK is used could set the region input field to an invalid value, potentially causing API requests to be misdirected.

Critical Impact
Applications using affected versions of AWS SDK for .NET may inadvertently route sensitive AWS API calls to attacker-controlled or non-AWS endpoints when malicious region values are supplied, potentially leading to information disclosure.

Affected Products

AWS SDK for .NET versions 4.0.0 to before 4.0.3.3

Discovery Timeline

2026-01-10 - CVE-2026-22611 published to NVD
2026-01-13 - Last updated in NVD database

Technical Details for CVE-2026-22611

Vulnerability Analysis

This vulnerability stems from improper input validation (CWE-20) in the AWS SDK for .NET. The SDK fails to adequately validate region input values before constructing AWS API endpoint URLs. When an application accepts user-controlled or environment-controlled region values without proper sanitization, an attacker with access to the application's environment can inject arbitrary values into the region field.

The attack requires network access and specific environmental conditions to be met, making exploitation complexity relatively high. However, successful exploitation could result in confidential data being exposed to unauthorized parties when API calls are routed to attacker-controlled endpoints instead of legitimate AWS infrastructure.

Root Cause

The root cause is insufficient input validation in the region parameter handling logic within the AWS SDK for .NET. The SDK did not properly validate that region values conform to legitimate AWS region identifiers before using them to construct service endpoint URLs. This allows specially crafted region strings to manipulate the destination of API requests.

Attack Vector

An attacker with access to the environment where the SDK operates could exploit this vulnerability by manipulating the region input field. This could be achieved through:

Setting malicious environment variables that the application uses for AWS region configuration
Modifying configuration files that specify the AWS region
Exploiting other application vulnerabilities to inject region values

When successful, AWS API calls intended for legitimate AWS endpoints would be routed to attacker-controlled hosts, potentially exposing sensitive request data including authentication credentials and API payloads.

The vulnerability requires specific conditions: the attacker must have access to modify the SDK's operating environment, and the application must use the compromised region value when making AWS API calls. For additional technical details, refer to the GitHub Security Advisory.

Detection Methods for CVE-2026-22611

Indicators of Compromise

Unusual AWS API calls being routed to non-standard endpoints
Network traffic to unexpected destinations from applications using AWS SDK for .NET
Log entries showing malformed or invalid region values in AWS API requests
Failed API calls due to certificate validation errors when SDK attempts to connect to non-AWS hosts

Detection Strategies

Monitor application logs for invalid or unexpected region values being used in AWS SDK configurations
Implement network monitoring to detect AWS API traffic being routed to non-AWS endpoints
Use runtime application security monitoring to detect manipulation of environment variables or configuration files
Audit code and configurations for hardcoded or externally-sourced region values

Monitoring Recommendations

Enable detailed logging for AWS SDK operations to capture region values used in API calls
Configure network egress monitoring to alert on connections to hosts outside expected AWS IP ranges
Implement configuration integrity monitoring to detect unauthorized changes to AWS SDK configuration sources
Deploy SentinelOne Singularity XDR for comprehensive endpoint and application behavior monitoring

How to Mitigate CVE-2026-22611

Immediate Actions Required

Upgrade AWS SDK for .NET to version 4.0.3.3 or later immediately
Audit all applications using AWS SDK for .NET versions 4.0.0 through 4.0.3.2
Review and restrict access to environment variables and configuration files that specify AWS regions
Validate that region values are sourced from trusted, immutable configurations

Patch Information

AWS has released version 4.0.3.3 of the AWS SDK for .NET which addresses this vulnerability by implementing proper validation of region input values. Organizations should update their applications to use the patched version as soon as possible. For detailed patch information, see the GitHub Security Advisory.

Workarounds

Implement application-level validation to ensure region values match known valid AWS region identifiers before passing them to the SDK
Hardcode AWS region values in application configuration rather than accepting them from external or user-controlled sources
Restrict environment access to prevent unauthorized modification of AWS SDK configuration parameters
Implement network-level controls to block outbound connections to non-AWS endpoints from systems running affected applications

bash

# Update AWS SDK for .NET using NuGet
dotnet add package AWSSDK.Core --version 4.0.3.3
# Or update all AWS SDK packages
dotnet list package --outdated | grep AWSSDK