Executive Summary

CVE-2026-5190 is a high-severity memory corruption vulnerability in the aws-c-event-stream library, which is part of the AWS Common Runtime. It occurs in the streaming decoder component before version 0.6.0. The flaw happens during the parsing of event-stream headers, where specially crafted messages sent by a third-party server can cause an out-of-bounds write, leading to memory corruption.

This memory corruption can potentially allow an attacker to execute arbitrary code on a client application that processes these malicious event-stream messages.

The vulnerability requires the attacker to control the server communicating with the client, and the client must process the crafted messages. AWS-operated servers are not vulnerable.

The issue was fixed in aws-c-event-stream version 0.6.0 by correcting the handling of buffer boundaries during decoding operations to prevent the overflow.

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Impact Analysis

If you use a client application that relies on vulnerable versions of aws-c-event-stream or dependent AWS SDKs, this vulnerability can allow a malicious third-party server to cause memory corruption in your client.

This memory corruption can lead to arbitrary code execution on your client application, potentially compromising the confidentiality, integrity, and availability of your system.

Exploitation requires the attacker to control the server sending event-stream messages and the client to process these messages, but no privileges are required on the client side.

To mitigate the risk, you should upgrade to aws-c-event-stream version 0.6.0 or later and update any dependent SDKs accordingly. Avoid connecting to untrusted servers using the event-stream protocol.

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Mitigation Strategies

To mitigate the CVE-2026-5190 vulnerability, users should upgrade aws-c-event-stream to version 0.6.0 or later.

Additionally, upgrade any higher-level AWS SDKs that depend on aws-c-event-stream to the fixed versions or later, including:

• aws-iot-device-sdk-cpp-v2 to version 1.42.1 or later
• aws-iot-device-sdk-java-v2 to version 1.30.1 or later
• aws-iot-device-sdk-python-v2 to version 1.28.2 or later
• aws-iot-device-sdk-js-v2 to version 1.25.1 or later
• aws-sdk-swift to version 1.6.70 or later
• aws-sdk-cpp to version 1.11.764 or later

As a workaround, avoid connecting to untrusted third-party servers using the event-stream protocol, since the vulnerability requires a malicious server to trigger.

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Compliance Impact

The provided information does not specify any direct impact of CVE-2026-5190 on compliance with common standards and regulations such as GDPR or HIPAA.

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Detection Guidance

There is no specific information provided in the available resources about detection methods or commands to identify this vulnerability on a network or system.

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