CVE-2026-18140 Amazon CVE debrief

Who should care

Users of aws-smithy-json, especially those who have smithy-rs generated servers, should be aware of this vulnerability and take action to remediate. This includes upgrading to aws-smithy-json version 0.62.7 or later. Operators, platform administrators, vulnerability management teams, and security teams should review the vulnerability details and plan for remediation.

Technical summary

CVE-2026-18140 involves uncontrolled recursion in the aws-smithy-json runtime crate before version 0.62.7. This issue affects smithy-rs generated servers and could allow remote unauthenticated users to cause a denial of service (process abort via stack exhaustion) through a small HTTP request with deeply nested JSON. The vulnerability has a HIGH CVSS score of 8.7, emphasizing the need for prompt remediation. Users should upgrade to aws-smithy-json 0.62.7 or later and rebuild affected systems. This issue is particularly concerning for operators, platform administrators, vulnerability management teams, and security teams who need to review the vulnerability details and plan for remediation. Evidence is limited to CVE and NVD details, highlighting the need for defensive verification tasks.

Defensive priority

High-priority defensive actions are required due to the HIGH CVSS score of 8.7 and potential for denial of service via stack exhaustion.

Recommended defensive actions

• Upgrade to aws-smithy-json 0.62.7 or later and rebuild.
• Review and update inventory to identify affected systems.
• Implement compensating controls to monitor for suspicious HTTP requests.
• Verify and test remediation on non-production environments before deployment.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.

Evidence notes

The CVE record indicates uncontrolled recursion in the aws-smithy-json runtime crate before 0.62.7, potentially allowing remote unauthenticated users to cause a denial of service via deeply nested JSON in a small HTTP request. Users should upgrade to aws-smithy-json 0.62.7 or later. Evidence is limited to CVE and NVD details.

Official resources