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High, CVSS 8.7amended

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

CVE-2026-18140GHSA-8ffr-xgwf-xj56

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (aws-smithy-json 0.62.7), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
8.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N · score source
EPSS
  • CVE-2026-18140: 0.78% estimated exploitation activity in the next 30 days; percentile 56.10 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-8ffr-xgwf-xj56

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GHSA-8ffr-xgwf-xj56

Agent brief

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# Patch Next advisory brief: CVE-2026-18140

Advisory: 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
IDs: CVE-2026-18140, GHSA-8ffr-xgwf-xj56
Record: https://patchnext.com/advisories/cve-2026-18140 (revision 3, source checked 26 Oct 2026, 15:43 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: aws-smithy-json 0.62.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io aws-smithy-json: affected <= 0.62.6; fixed in 0.62.7

## Suggested inspection (read-only)
- crates.io aws-smithy-json: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on aws-smithy-json.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-8ffr-xgwf-xj56 (OSV record GHSA-8ffr-xgwf-xj56 lists affected ranges: crates.io aws-smithy-json >=0 <0.62.7 (fixed))
- Verified: https://github.com/advisories/GHSA-8ffr-xgwf-xj56 (GitHub-reviewed advisory GHSA-8ffr-xgwf-xj56 lists affected ranges: crates.io aws-smithy-json >=0 <=0.62.6)

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