---
id: CVE-2026-18140
aliases:
  - GHSA-8ffr-xgwf-xj56
title: >-
  aws-smithy-json: Uncontrolled recursion in the aws-smithy-json unknown-key
  skip path allows unauthenticated remote denial of service in smithy-rs
  generated servers
summary: >-
  aws-smithy-json: Uncontrolled recursion in the aws-smithy-json unknown-key
  skip path allows unauthenticated remote denial of service in smithy-rs
  generated servers
severity: high
cvss: 7.5
cwe:
  - CWE-674
vendor: aws-smithy-json
product: aws-smithy-json
ecosystem: rust
affected:
  - aws-smithy-json <= 0.62.6
patched:
  - aws-smithy-json 0.62.7
published: '2026-10-02'
updated: '2026-10-02'
sourceUpdated: '2026-10-02T22:44:53Z'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-8ffr-xgwf-xj56'
references:
  - url: >-
      https://github.com/smithy-lang/smithy-rs/security/advisories/GHSA-8ffr-xgwf-xj56
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-18140'
  - url: 'https://github.com/smithy-lang/smithy-rs/pull/4685'
  - url: >-
      https://github.com/smithy-lang/smithy-rs/commit/8f0882046c467981ba5b4fd91a10befa96bd262f
  - url: 'https://aws.amazon.com/security/security-bulletins/2026-067-aws'
  - url: 'https://crates.io/crates/aws-smithy-json/0.62.7'
  - url: 'https://github.com/advisories/GHSA-8ffr-xgwf-xj56'
tags:
  - ghsa
  - rust
epss: 0.00431
epssPercentile: 0.35016
ingestedAt: '2026-10-02T23:34:57.399Z'
---

## Overview

### Summary
Smithy-RS is a Rust code generation and runtime framework that generates HTTP clients and servers from Smithy interface definitions, powering the AWS SDK for Rust and custom service implementations. An issue exists which allows uncontrolled recursion in the unknown-key skip path of the Amazon aws-smithy-json runtime crate in versions 0.62.6 and earlier.

### Impact
Uncontrolled recursion in the unknown-key skip path of the aws-smithy-json runtime crate before 0.62.7, which the smithy-rs code generator invokes from every generated struct deserializer, might allow remote unauthenticated users to cause a denial of service (process abort via stack exhaustion) via a single small HTTP request containing deeply nested JSON to a smithy-rs generated server.

Impacted versions: aws-smithy-json <= 0.62.6

### Patches
This issue has been addressed in aws-smithy-json version 0.62.7. We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.

### Workarounds
There are no workarounds besides updating to the patched version.

### References
If you have any questions or comments about this advisory, AWS asks that you contact [AWS/Amazon] Security via their [vulnerability reporting page](https://aws.amazon.com/security/vulnerability-reporting) or directly via email to [aws-security@amazon.com](mailto:aws-security@amazon.com). Please do not create a public GitHub issue.

## Affected packages

- `aws-smithy-json <= 0.62.6`

## Remediation

Upgrade to a patched release:

- `aws-smithy-json 0.62.7`