CVE-2026-16756 - Allocation of resources without limits in the default aws-smithy-http-server serve() path allows unauthenticated Slowloris denial of service

unknownCVE-2026-16756

Bulletin ID: 2026-064-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 07/23/2026 11:30 AM PDT Description: 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. We identified CVE-2026-16756 where the allocation of resources without limits in the default aws-smithy-http-server serve() path allows unauthenticated "Slowloris" denial of service. Impacted versions: aws-smithy-http-server <= 0.66.4 Please refer to the article below for the most up-to-date and complete information related to this AWS Security Bulletin.

CSIRTS triage

vendor: AWS product: aws-smithy-http-server Denial of serviceaffected: <= 0.66.4

What: The allocation of resources without limits allows unauthenticated Slowloris denial of service.
Who is affected: Deployments of aws-smithy-http-server version 0.66.4 and earlier.
Urgency: Remediation is important as it allows for denial of service attacks.
Action: Update to a version greater than 0.66.4.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: AWS Security Bulletins (INTL · vendor-psirt · site)
Severity: unknown
Published: 2026-08-20
Exploitation: Not in CISA KEV at last sync

Original advisory: https://aws.amazon.com/security/security-bulletins/rss/2026-064-aws/

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-167560.42% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 35% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-16756	coverage & exploitation status	NVD · CVE.org

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