AWS Advises of Heap Double-Free Vulnerability in Common Runtime HTTP Component

Amazon Web Services disclosed CVE-2026-12043, a heap double-free flaw in its Common Runtime library that could impact services using aws-c-http.

Threat Times Exposure DeskOctober 9, 20262 min read

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Illustration: A translucent glass jar containing neatly stacked blue memory blocks sits on a plain white desk. — AI-generated illustration: Threat Times

Key points

AWS identified CVE-2026-12043 as a heap double-free vulnerability within the aws-c-http component.
The flaw resides in the AWS Common Runtime, a foundational library for many Amazon Web Services.
The security bulletin highlights the technical nature of the defect without specifying affected customer accounts.

Amazon Web Services (AWS) has issued a security bulletin identifying CVE-2026-12043, a heap double-free vulnerability within its Common Runtime infrastructure. The advisory specifically targets the aws-c-http component, a critical module responsible for handling HTTP communications across various AWS services and tools.

The vulnerability stems from improper memory management within the aws-c-http library. A heap double-free error occurs when a program attempts to free the same block of memory twice, which can lead to undefined behavior, application crashes, or potentially allow an attacker to manipulate memory structures. This type of flaw is significant in low-level runtime libraries because they often underpin high-throughput services where memory safety is paramount.

Context and Background

The AWS Common Runtime (CRT) is a collection of libraries designed to provide high-performance, portable, and secure implementations of common networking and cryptographic functions. These libraries are used extensively across the AWS ecosystem, including in the AWS SDKs for various programming languages, the AWS Command Line Interface (CLI), and internal AWS services.

By identifying this vulnerability in the aws-c-http module, AWS is addressing a risk that could theoretically affect any service or application relying on this specific component for HTTP traffic handling. The disclosure follows standard responsible disclosure practices, aiming to inform users of the technical defect so they can assess their exposure. The bulletin does not detail a specific exploit scenario or active wild exploitation, but rather focuses on the technical classification of the memory safety issue.

Memory safety vulnerabilities like heap double-frees are common targets for security researchers and attackers due to their potential to be leveraged for remote code execution or denial-of-service conditions. The severity of such issues depends largely on whether the vulnerable component is exposed to untrusted input and how easily an attacker can trigger the double-free condition.

Who is Affected

Because the AWS Common Runtime is a foundational library, the potential impact of CVE-2026-12043 is broad. Any system or application utilizing the aws-c-http component from the affected versions of the Common Runtime is technically exposed to this vulnerability. This includes developers using AWS SDKs that bundle the CRT, as well as AWS-managed services that rely on this underlying library for network communications.

AWS typically provides guidance on which specific SDK versions or service endpoints are impacted in subsequent updates to the security bulletin. Until further details are released, users should assume that any deployment using the standard AWS HTTP client implementations may be relevant. The primary concern for security teams is to determine if their architectures expose the aws-c-http module to untrusted network traffic that could trigger the double-free condition.

What should you do?

Security professionals should monitor the AWS Security Bulletins RSS feed and the official AWS Security Center for updates regarding this advisory. While the initial bulletin identifies the flaw, it does not yet confirm the availability of a patched version or specific remediation steps for all affected components.

Organizations should review their dependency lists to identify usage of the AWS Common Runtime and the aws-c-http module. It is advisable to restrict network access to internal services using this library until a patch is confirmed, minimizing the attack surface for potential exploitation. Additionally, enabling detailed logging and monitoring for abnormal HTTP behavior or application crashes can help detect any attempts to leverage this vulnerability.

What to do and how to stay safe: AWS

Audit your infrastructure to identify all instances where the AWS Common Runtime and aws-c-http component are deployed.
Restrict network ingress to services relying on this library to trusted sources only, reducing the risk of triggering the vulnerability.
Monitor application logs for unexpected crashes or memory errors that could indicate exploitation attempts.
Subscribe to AWS security updates to receive immediate notification when a patched version of the library becomes available.

Step-by-step guide: Risk Based Vulnerability Management: Prioritize Fixes by Actual Threat

General security guidance from the Threat Times newsroom. It is not confirmed advice from the organisations named in this story.