Vulnerability-Lookup

GHSA-29W2-FQ35-V728

Vulnerability from github – Published: 2026-07-24 22:33 – Updated: 2026-07-24 22:33

Summary

AWS API MCP Server Security Policy Bypass via Startup Initialization Failure

Details

Summary

The AWS API MCP Server is an open source Model Context Protocol (MCP) server that enables AI assistants to interact with AWS services and resources through AWS CLI commands. It provides programmatic access to manage your AWS infrastructure while maintaining proper security controls. It includes an optional, user-configured security policy that can deny or gate specific AWS operations. An issue exists where, if the data used to enforce this policy fails to initialize at server startup, the per-request policy check is silently skipped for the lifetime of the process.

Impact

On startup, the server loads data used to enforce the configured security policy. If that load fails, the server continues running without the enforcement data in place. In the default configuration, the per-request security check is then bypassed for the lifetime of the process: configured deny and gate rules are not consulted, and AWS API operations the policy was intended to restrict execute without enforcement. The scope is limited to the security-policy gate; IAM permissions on the configured credentials remain in effect and continue to bound what the server can do.

Impacted versions: >= 0.2.13 AND < 1.3.47

Patches

This issue has been addressed in awslabs.aws-api-mcp-server version 1.3.47. AWS recommends upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.

Workarounds

Any one of the following prevents the bypass until you can upgrade:

Use least-privilege IAM credentials (for example, a ReadOnlyAccess role) scoped to the task. IAM remains the primary access control and is enforced regardless of this issue.
If the server started during degraded connectivity, restart it once connectivity is restored so the policy enforcement data loads successfully.

Contact

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

Acknowledgement

We would like to thank Lav Kumar Vishwakarma (independent security researcher) for collaborating on this issue through the coordinated vulnerability disclosure process.

Severity

7.0 (High)


                  
                    CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

7.3 (High)


                  
                    CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Show details on source website

JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "awslabs.aws-api-mcp-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.2.13"
            },
            {
              "fixed": "1.3.47"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-16584"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-455"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-24T22:33:19Z",
    "nvd_published_at": "2026-07-23T16:17:15Z",
    "severity": "HIGH"
  },
  "details": "## Summary\nThe AWS API MCP Server is an open source Model Context Protocol (MCP) server that enables AI assistants to interact with AWS services and resources through AWS CLI commands. It provides programmatic access to manage your AWS infrastructure while maintaining proper security controls. It includes an optional, user-configured security policy that can deny or gate specific AWS operations. An issue exists where, if the data used to enforce this policy fails to initialize at server startup, the per-request policy check is silently skipped for the lifetime of the process.\n\n### Impact\nOn startup, the server loads data used to enforce the configured security policy. If that load fails, the server continues running without the enforcement data in place. In the default configuration, the per-request security check is then bypassed for the lifetime of the process: configured deny and gate rules are not consulted, and AWS API operations the policy was intended to restrict execute without enforcement. The scope is limited to the security-policy gate; IAM permissions on the configured credentials remain in effect and continue to bound what the server can do.\n\n**Impacted versions**: \u003e= 0.2.13 AND \u003c 1.3.47\n\n### Patches\nThis issue has been addressed in awslabs.aws-api-mcp-server version 1.3.47. AWS recommends upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.\n\n### Workarounds\nAny one of the following prevents the bypass until you can upgrade:\n\n  - Use least-privilege IAM credentials (for example, a ReadOnlyAccess role) scoped to the task. IAM remains the primary access control and is enforced regardless of this issue.\n  - If the server started during degraded connectivity, restart it once connectivity is restored so the policy enforcement data loads successfully.\n\n### Contact\nIf you have any questions or comments about this advisory, AWS asks that you contact AWS Security via the [reporting page](https://aws.amazon.com/security/vulnerability-reporting) or directly via email to [aws-security@amazon.com](mailto:aws-security@amazon.com). Please do not create a public GitHub issue.\n\n### Acknowledgement\nWe would like to thank Lav Kumar Vishwakarma (independent security researcher) for collaborating on this issue through the coordinated vulnerability disclosure process.",
  "id": "GHSA-29w2-fq35-v728",
  "modified": "2026-07-24T22:33:19Z",
  "published": "2026-07-24T22:33:19Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/awslabs/mcp/security/advisories/GHSA-29w2-fq35-v728"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-16584"
    },
    {
      "type": "WEB",
      "url": "https://github.com/awslabs/mcp/pull/4315"
    },
    {
      "type": "WEB",
      "url": "https://github.com/awslabs/mcp/commit/ab1bbebc097d674c1cdd4bd75a8f313be18473bf"
    },
    {
      "type": "WEB",
      "url": "https://aws.amazon.com/security/security-bulletins/2026-063-aws"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/awslabs/mcp"
    },
    {
      "type": "WEB",
      "url": "https://pypi.org/project/awslabs.aws-api-mcp-server/1.3.47"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "AWS API MCP Server Security Policy Bypass via Startup Initialization Failure"
}

CVE-2026-16584 (GCVE-0-2026-16584)

Vulnerability from cvelistv5 – Published: 2026-07-23 15:34 – Updated: 2026-07-23 18:16

Title

AWS API MCP Server Security Policy Bypass via Startup Failure

Summary

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.

Severity

7 (High)


                        
                          CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

7.3 (High)


                        
                          CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator (v2.0.3)

CWE

CWE-455 - Non-exit on failed initialization

Assigner

AMZN

References

3 references

URL	Tags
https://pypi.org/project/awslabs.aws-api-mcp-serv…	release-notespatch
https://aws.amazon.com/security/security-bulletin…	vendor-advisory
https://github.com/awslabs/mcp/security/advisorie…	release-notes

Impacted products

1 product

Vendor	Product	Version
AWS	aws-api-mcp-server	Affected: 0.2.13 , < 1.3.47 (custom)

Show details on NVD website

JSON

To clipboard

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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-29W2-FQ35-V728

Summary

Impact

Patches

Workarounds

Contact

Acknowledgement

CVE-2026-16584 (GCVE-0-2026-16584)

Tags

Sightings

Nomenclature