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CVE-2026-42559

RMCP: DNS rebinding vulnerability in rmcp Streamable HTTP server transport

Published: May 14, 2026Updated: May 14, 2026 Sources: CVE List NVDCWE-346
NVD MITRE
8.8CVSSHIGH
EPSS Score
0.2%
Top 88.6%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available

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.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:RS:UC:HI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:RUser Interaction
Required
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
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Weaknesses

CWE-346CWE-350

Affected Products

rust-sdkmodelcontextprotocol
Mixed
AI / ML / ai-agent-tooling
modelcontextprotocoloss-projectAI / MLaka mcp, model context protocol

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

References

https://github.com/modelcontextprotocol/rust-sdk/commit/8e22aa2de28df5a285eed87c11cd89bf15fa90d3
github.com
https://github.com/modelcontextprotocol/rust-sdk/issues/815
github.com
https://github.com/modelcontextprotocol/rust-sdk/issues/822
github.com
and 2 more references View all →

Timeline

Published
May 14, 2026
Last Updated
May 14, 2026

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