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The issue involves the AWS SDK for Rust’s handling of the region input field when constructing endpoint URLs for AWS API calls. An actor with access to the application’s environment—such as through environment variables, configuration files, or code injection—could set the region to an invalid value. This region value is used directly to build the endpoint URL, typically in the form “https://service.region.amazonaws.com”. If the region contains characters that are not valid host label components, like special characters or multiple dots, the resulting URL may become malformed. This could cause the HTTP client to attempt connections to non-existent or non-AWS hosts, such as domains controlled by the actor if the region value mimics a domain. For example, setting region to “attacker.com” might route calls to “https://service.attacker.com.amazonaws.com”, which could resolve to a malicious site if DNS is poisoned. The SDK prior to the patch did not validate that the region string conforms to host label standards: it must contain only alphanumeric characters and hyphens, cannot start or end with a hyphen, and must not be empty. This lack of validation allowed for potential injection attacks where the region could alter the URL structure, leading to misrouted traffic. While this requires the actor to have significant access to the environment, it represents a defense-in-depth gap. The enhancement adds validation to ensure the region is a valid host label before URL construction, preventing such manipulations.
Platform: AWS SDK Rust
Version: Before 2025-11-06
Vulnerability: Region validation bypass
Severity: Informational
Date: 2025-11-06
Prediction: Patched 2025-11-06
What Undercode Say:
Analytics:
bash commands:
cargo pkgid aws-sdk
cargo update aws-sdk
git clone smithy-rs
Codes:
fn validate_region(region: &str) -> bool {
let re = Regex::new(r”^[a-zA-Z0-9][a-zA-Z0-9-][a-zA-Z0-9]$”).unwrap();
re.is_match(region) && !region.is_empty()
}
How Exploit:
Set AWS_REGION environment variable to invalid value like “malicious.com”. SDK constructs incorrect endpoint URLs. Calls route to non-AWS hosts.
Protection from this CVE
Update AWS SDK. Validate region input. Follow AWS best practices.
Impact:
Improper API routing. Denial of service. Potential data exposure.
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Sources:
Reported By: github.com
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