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CVE-2026-34742

8.1 · HIGH

The Go MCP SDK used Go's standard encoding/json.

Published Apr 2, 2026CWE-1188EPSS 0.66%

Overview

CVE-2026-34742 is a high-severity vulnerability. It was published on April 2, 2026 and has a CVSS 3.1 base score of 8.1 (HIGH).

This vulnerability has a CVSS 3.1 base score of 8.1, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

The Go MCP SDK used Go's standard encoding/json. Prior to version 1.4.0, the Model Context Protocol (MCP) Go SDK does not enable DNS rebinding protection by default for HTTP-based servers. When an HTTP-based MCP server is run on localhost without authentication with StreamableHTTPHandler or SSEHandler, a malicious website could exploit DNS rebinding to bypass same-origin policy restrictions and send requests to the local MCP server. This could allow an attacker to invoke tools or access resources exposed by the MCP server on behalf of the user in those limited circumstances. This issue has been patched in version 1.4.0.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976cdb8ff1e986b6dGitHubgithub.com/modelcontextprotocol/go-sdk/pull/760GitHubgithub.com/modelcontextprotocol/go-sdk/releases/tag/v1.4.0GitHubgithub.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-xw59-hvm2-8pj6Refaccess.redhat.com/errata/RHSA-2026:21772Refaccess.redhat.com/security/cve/CVE-2026-34742Refbugzilla.redhat.com/show_bug.cgi?id=2454608Refsecurity.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34742.json

How CyberStrike helps

Frequently asked questions

What is CVE-2026-34742?

CVE-2026-34742 is a high-severity vulnerability. It was published on April 2, 2026 and has a CVSS 3.1 base score of 8.1 (HIGH).

How severe is CVE-2026-34742?

This vulnerability has a CVSS 3.1 base score of 8.1, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-34742?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-34742?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-34742 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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