Is CVE-2026-42559 actively exploited?

No active exploitation of CVE-2026-42559 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-42559 be exploited remotely?

Yes. CVE-2026-42559 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-42559?

CVE-2026-42559 has a CVSS score of 8.8 (HIGH).

HOME VULNERABILITIESCVE-2026-42559

HIGH

CVE-2026-42559

CWE-346Published: May 14, 2026· Updated: May 14, 2026

8.8

CVSS v3.1

EPSS:0.02%probability of exploitation in 30 daysPercentile:4.8th

Official Description

RMCP is an official Rust SDK for the Model Context Protocol. Prior to version 1.4.0, the rmcp crate's Streamable HTTP server transport (crates/rmcp/src/transport/streamable_http_server/) did not validate the incoming Host header. This allowed a malicious public website, via a DNS rebinding attack, to send authenticated requests to an MCP server running on the victim's loopback or private-network interface. This vulnerability is fixed in 1.4.0.

NVD Source

Technical Analysis

CVE-2026-42559 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation does not require any privileges, though user interaction (Required) is needed, which slightly reduces the risk of mass automated attacks.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 8.8.