CVE-2026-125271: Auth Bypass (CVSS 7.8)

Description

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.

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CVSS v3.1 Score

7.8

HIGH

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

EPSS — Exploit Prediction

0.0037

Probability of exploitation

0.32%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-863 Incorrect Authorization

CWE-1025 CWE-1025

References

Other References

https://aws.amazon.com/security/security-bulletins/2026-176-aws/ https://github.com/awslabs/mcp/security/advisories/GHSA-4wq9-grf3-qg2p https://pypi.org/project/awslabs.aws-api-mcp-server/1.5.1/

Frequently Asked Questions

What is CVE-2026-125271? +

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. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2026-125271? +

CVE-2026-125271 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0037, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-125271? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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