AWS SDK for .NET V4 adopted defense in depth enhancement for region parameter value

CVE-2026-22611 → View on GitHub ↗ View on CVE.org ↗ View on NVD ↗

Description

Summary

This notification is related to the use of specific values for 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.

A defense-in-depth enhancement has been implemented in the AWS SDK for .NET v4. This enhancement validates that a region used to construct an endpoint URL is a valid host label. The change was released on Nov 21, 2025. This advisory is informational to help customers understand their responsibilities regarding configuration security.

Impact

Customer applications could be configured to improperly route AWS API calls to non-existent or non-AWS hosts. While the SDK was functioning safely within the requirements of the shared responsibility model, additional safeguards have been added to support secure customer implementations.

Impacted versions: All versions of the AWS SDK for .NET V4 prior to the 4.0.139.0 release (the AWS SDK for .NET V3 was not impacted)

Patches

On Nov 21, 2025, an enhancement [1] was made to the AWS SDK for .NET v4 release, which validates the formatting of a region, providing additional safeguards.

Workarounds

No workarounds are needed, but as always developers should ensure that their application is following security best practices:
- Implement proper input validation in your application code
- Update to the latest AWS SDK for .NET release on a regular basis
- Follow AWS security best practices [2] for SDK configuration

References

Contact AWS Security via the vulnerability reporting page or email [email protected].

Acknowledgement

AWS SDK for .NET v4 thanks Guy Arazi for bringing these customer security considerations to our attention through the coordinated disclosure process.

[1] https://github.com/aws/aws-sdk-net/pull/4150

[2] https://docs.aws.amazon.com/sdk-for-net/v4/developer-guide/security.html

Basic information

Type
reviewed
Severity
low
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2026-01-09 18:56:21 UTC
Updated
2026-01-11 14:56:01 UTC
GitHub reviewed
2026-01-09 18:56:21 UTC
NVD published
2026-01-10

EPSS Score

Score Percentile
0.06% 18.75%

CVSS Scores

Base score Version Severity Vector
3.7 3.1 —
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.

Identifiers

Type Value
GHSA GHSA-9cvc-h2w8-phrp ↗
CVE CVE-2026-22611 ↗

CWEs

CWE id Name
CWE-20 Improper Input Validation

Affected packages (1)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
nuget AWSSDK.Core >= 4.0.0, < 4.0.3.3 4.0.3.3 —

References

cvelogic Threat Intelligence