# CVE-2026-125271: AWS API MCP Server Security Policy Bypass via Incorrect Operation Name Normalization

Status: published. Published: 2026-11-10. Updated: 2026-11-10.

Incorrect normalization of operation names in the custom security policy enforcement in awslabs aws-api-mcp-server before 1.5.1 might allow an actor to execute AWS API operations across AWS services that the operator's security policy was configured to deny or require elicitation for, via calls to operations whose names contain consecutive capital letters.



To remediate this issue, users should upgrade to version 1.5.1.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: AMZN) — https://pypi.org/project/awslabs.aws-api-mcp-server/1.5.1/

## Affected products and versions

- AWS / aws-api-mcp-server: ≥ 0.2.13; < 1.5.1 (affected, custom). Source: CNA: AMZN

## Severity and prioritization

- CVSS 3.1: 7.8 (high); CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H; source: CNA: AMZN

- CVSS 4.0: 8.5 (high); CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N; source: CNA: AMZN

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-1025, CWE-863

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://pypi.org/project/awslabs.aws-api-mcp-server/1.5.1/ (CNA: AMZN; release-notes, patch)

- https://aws.amazon.com/security/security-bulletins/2026-176-aws/ (CNA: AMZN; vendor-advisory)

- https://github.com/awslabs/mcp/security/advisories/GHSA-4wq9-grf3-qg2p (CNA: AMZN; third-party-advisory)

## Provenance

- CNA: AMZN: https://www.cve.org/CVERecord?id=CVE-2026-125271; retrieved 2026-11-10; source updated 2026-11-10

Revision: 46e3742de4d8714b959955446c392e8e5b42f76cad14a7e82686f23b3f3d013c

Canonical: https://y2.dev/cve/CVE-2026-125271

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