4.3

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2025-9039

CVE-2025-9039: Information Disclosure in Amazon ECS Container Agent

Summary Amazon Elastic Container Service (Amazon ECS) is a fully managed container orchestration service that enables customers to deploy, manage, and scale containerized applications. Amazon ECS container agent provides an introspection API that provides information about the overall state of the Amazon ECS agent and the container instances.

We identified CVE-2025-9039, an issue in the Amazon ECS agent.

Impact Under certain conditions, this issue could allow an introspection server to be accessed off-host by another instance if the instances are in the same security group or if their security groups allow incoming connections that include the port where the server is hosted. This issue does not affect instances where the option to allow off-host access to the introspection server is set to 'false'.

Impacted versions: version 0.0.3 through 1.97.0

Patches This issue has been addressed in ECS agent version 1.97.1. We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.

Workarounds Customers who cannot update to the latest AMI can modify the Amazon EC2 security groups to restrict incoming access to the introspection server port (51678).

References If you have any questions or comments about this advisory, we ask that you contact AWS Security via our vulnerability reporting page or directly via email to aws-security@amazon.com. Please do not create a public GitHub issue.

(GitHub Advisory)

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CVE-2025-9039

CVE-2025-9039:

4.3

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
github.com/aws/amazon-ecs-agent	go	>= 0.0.3, <= 1.97.0	1.97.1

Technical Details

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Root Cause Analysis

The vulnerability, CVE-2025-9039, allows for an information disclosure in the Amazon ECS Container Agent due to improper validation of IPv6 configuration before applying firewall rules. The introspection server, which provides metadata about the agent and container instances, could be accessed from off-host if IPv6 was enabled but not fully configured on the host, causing ip6tables rules to fail silently.

The analysis of the patch between version 1.97.0 (vulnerable) and 1.97.1 (patched) revealed that the core of the fix lies within the ecs-init/exec/iptables/iptables.go file. Specifically, the modifyNetfilterEntry function was modified to include a check for the existence of the IPv6 kernel configuration before attempting to apply ip6tables rules. This prevents the agent from leaving the introspection server's IPv6 endpoint unprotected.

The primary vulnerable function is iptables.NetfilterRoute.modifyNetfilterEntry, as it contained the flawed logic. The iptables.NetfilterRoute.Create function is also identified as a key function, as it is the entry point that triggers the vulnerable logic during the agent's startup and firewall setup. The addition of the iptables.checkIpv6KernelConfigExist function in the patch is the direct mitigation for the vulnerability.

An engineer with this CVE in their environment should understand that the risk lies in environments where IPv6 is enabled at the OS level but not fully configured, which could lead to the exposure of sensitive instance and container metadata. The recommended action is to upgrade the ECS agent to version 1.97.1 or later, or, as a workaround, to use security groups to restrict access to the introspection server port (51678).

Vulnerable functions

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WAF Rule

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Reasoning

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