Is CVE-2026-4270 in the CISA KEV catalog?

No. CVE-2026-4270 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-4270?

CVE-2026-4270 has a CVSS v3 base score of 5.5 (MEDIUM).

What is the EPSS score for CVE-2026-4270?

CVE-2026-4270 has an EPSS score of 0.13% (3th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-4270?

Upgrade aws api mcp server to 1.3.9 or later.

CVE & CISA-KEV Catalog

CVE-2026-4270

MEDIUM

5.5

CVSS v3

NVD

Description

Improper Protection of Alternate Path exists in the no-access and workdir feature of the AWS API MCP Server versions >= 0.2.14 and < 1.3.9 on all platforms may allow the bypass of intended file access restriction and expose arbitrary local file contents in the MCP client application context. To remediate this issue, users should upgrade to version 1.3.9.

CWE-424

How to fix

Remediation Available

aws api mcp serverNVD

Affected:>= 0.2.14, < 1.3.9Fixed in:1.3.9CVE-2026-4270derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorLocal

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityNone

AvailabilityNone

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

Exploit Intelligence

0.13%probability of exploitation in 30 days

3rdpercentile

Low risk: more likely to be exploited than 3% of all known CVEs.

References

Vendor Advisory1

aws.amazon.com

Third-Party Advisory1

pypi.org

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-21.