High 8.8Published May 14, 2026

CVE-2026-42559RMCP: DNS rebinding vulnerability in rmcp Streamable HTTP server transport

Updated under an hour ago (Oct 27, 2026, 4:50 AM ET)

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It affects modelcontextprotocol rust-sdk. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for modelcontextprotocol rust-sdk

Exploited in the last 30 days

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.

CVSS: 8.8 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-346, CWE-350
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: May 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

modelcontextprotocol rust-sdk modelcontextprotocol:rust_sdk (from the name)	before 1.4.0	CNA record

References

References

https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-89vp-x53w-74fx	x-refsource-confirm
https://github.com/modelcontextprotocol/rust-sdk/issues/815	x-refsource-misc
https://github.com/modelcontextprotocol/rust-sdk/issues/822	x-refsource-misc
https://github.com/modelcontextprotocol/rust-sdk/pull/764	x-refsource-misc
https://github.com/modelcontextprotocol/rust-sdk/commit/8e22aa2de28df5a285eed87c11cd89bf15fa90d3	x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.