CVE-2026-22611 — AWSSDK.Core
LOWCVE-2026-22611 is a low-severity (CVSS 3.7) Improper Input Validation vulnerability in AWSSDK.Core. A fix is available for AWSSDK.Core — see the affected versions and patch details below.
AWS SDK for .NET V4 adopted defense in depth enhancement for region parameter value
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-22611.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-22611 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
AWSSDK.CoreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.
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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | AWSSDK.Core | ≥ 4.0.0&&< 4.0.3.3 | 4.0.3.3dotnet add package AWSSDK.Core --version 4.0.3.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for AWSSDK.Core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update AWSSDK.Core to 4.0.3.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-22611 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-22611 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-22611. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-22611 in your dependencies?
O3 Security finds CVE-2026-22611 across NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.