CVE-2026-16756 in aws-smithy-http-server
Summary
by MITRE • 07/23/2026
Missing connection and header-read timeouts and the absence of a concurrent-connection cap in the default serve() path of Amazon aws-smithy-http-server might allow remote attackers to cause a denial of service by opening many connections and sending partial requests that are never completed, exhausting server sockets and tasks.
To mitigate this issue, users should upgrade to aws-smithy-http-server 0.66.5 or later.
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Analysis
by VulDB Data Team • 07/23/2026
The vulnerability described in the CVE relates to insufficient resource management within the default serve() path of Amazon's aws-smithy-http-server library. This flaw creates a significant denial of service risk by allowing remote attackers to exploit the absence of proper timeout mechanisms and connection limits. The root cause stems from missing configuration parameters that should govern how the server handles incoming connections and request processing. Without established timeouts for both connection establishment and header reading phases, malicious actors can maintain numerous open connections that remain inactive or partially completed indefinitely.
The technical implementation of this vulnerability exploits fundamental HTTP server resource exhaustion patterns where attackers establish multiple connections to the server without completing the request lifecycle. This behavior creates a scenario where server resources become consumed by connections that are never properly closed or processed, leading to socket exhaustion and task queue saturation. The absence of concurrent connection caps means there is no upper boundary on active connections, allowing an attacker to scale their resource consumption linearly with available server capacity. This type of vulnerability aligns with CWE-400 which categorizes unchecked resource consumption as a critical weakness in application security.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire server infrastructure. When connection limits are not enforced, servers can quickly exhaust their available file descriptors, memory resources, and thread pools, resulting in complete service unavailability for legitimate users. This attack vector is particularly dangerous because it requires minimal resources to execute and can be automated at scale, making it an attractive method for distributed denial of service attacks. The vulnerability affects the core serving functionality of the aws-smithy-http-server library, meaning any application built using this component is potentially exposed to this risk.
The recommended mitigation involves upgrading to aws-smithy-http-server version 0.66.5 or later, which includes proper timeout configurations and connection limiting mechanisms. This upgrade addresses the fundamental architectural weakness by implementing proper resource management controls that were previously absent from the default configuration. The fix typically incorporates configurable timeouts for both connection establishment and header reading phases, along with maximum concurrent connection limits that prevent resource exhaustion attacks. Organizations should also consider implementing additional monitoring and alerting around connection counts and resource utilization to detect potential exploitation attempts before they cause significant service disruption.
This vulnerability demonstrates the critical importance of proper resource management in HTTP server implementations and aligns with ATT&CK technique T1499 which covers network denial of service attacks. The remediation approach follows security best practices outlined in OWASP Top Ten and NIST cybersecurity guidelines for preventing resource exhaustion attacks. Organizations should also review their application configurations to ensure that timeout values are appropriately tuned for their specific use cases and that connection pooling parameters are properly configured to prevent similar vulnerabilities in other components of their infrastructure stack.