CVE•Published 2026-05-27•Modified 2026-05-29•0 articles on news•6 live references•NVD data

CVE-2026-9739

Vulnerability data via NVD (ingested)

CVSS v3.1

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EPSS percentile

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Weaknesses (CWE)

CWE-942Permissive Cross-domain Security Policy with Untrusted Domains

Description

Vulnerable to DNS rebinding attacks when using SSE (http://b/499408790). During the beta phase, we implemented `allowed-origins` and `allowed-hosts` flags to align with MCP security guidelines. However, the hardcoded `Access-Control-Allow-Origin: *` header in the SSE initialization handler was inadvertently retained. This vulnerability specifically impacts users connecting via Toolbox using SSE under specification v2024-11-05.

Timeline

Published 2026-05-27

Modified 2026-05-29

External references

NVD MITRE Exploit-DB GitHub PoC Sploitus VulnCheck

Search for exposed instances

Shodan + Censys queries derived from NVD's CPE data. The vuln tag catches assets Shodan has explicitly linked to this CVE; the product / banner fingerprints find exposed instances even when the vuln tag was never applied (which is common).

Shodan · vuln tag0 hosts

vuln:CVE-2026-9739

Hosts Shodan has explicitly fingerprinted as vulnerable.

More intel sources (5)

Shodan report

vuln:CVE-2026-9739

Country / ASN / product breakdown for the vuln query.

Censys

vulnerabilities.cve_id: CVE-2026-9739

Censys host search filtered to this CVE id.

grep.app

CVE-2026-9739