CVE-2026-34742Network attack vector

Tool invocation via unvalidated rebinding Host headers

Published Apr 2, 2026 · Updated Apr 2, 2026

DNS rebinding in the Model Context Protocol Go SDK before 1.4.0 allows remote attackers to invoke tools through local HTTP servers. StreamableHTTPHandler and SSEHandler accepted requests arriving over loopback without verifying that the Host header also named a loopback address. Exploitation requires an unauthenticated localhost deployment and a user to visit attacker-controlled web content; stdio transport is unaffected, and exposed tools or resources determine the resulting access.

CVSS severity7.6
High
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

DNS rebinding in the Model Context Protocol Go SDK before 1.4.0 allows remote attackers to invoke tools through local HTTP servers. StreamableHTTPHandler and SSEHandler accepted requests arriving over loopback without verifying that the Host header also named a loopback address. Exploitation requires an unauthenticated localhost deployment and a user to visit attacker-controlled web content; stdio transport is unaffected, and exposed tools or resources determine the resulting access.

The record

CVE
CVE-2026-34742
Published
Apr 2, 2026
Updated
Apr 2, 2026
Vendor
Model Context Protocol
Product
Go SDK
Classifications
CWE-1188, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.4.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Model Context Protocol · Go SDKversion=< 1.4.0

Published CVSS scores

8.0Red Hat Product SecurityCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N
8.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
7.6GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1188Initialization of a Resource with an Insecure Default
T1189Drive-by Compromise

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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