CVE-2026-42559
RMCP: DNS rebinding vulnerability in rmcp Streamable HTTP server transport
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
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.
Timeline
ID reserved
By GitHub_M
- 16 days later
· 16 days later
Published
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High8.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H |
| NVDNVD · Deferred | 3.1 | High8.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.27% · top 81% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.8.
Weakness
Affected products
modelcontextprotocol · rust-sdk
- affected < 1.4.0
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- crates.iormcpGHSA-89vp-x53w-74fx (opens in a new tab)
References (5)
- https://github.com/modelcontextprotocol/rust-sdk/security/advisories/GHSA-89vp-x53w-74fx (opens in a new tab)x_refsource_CONFIRM
- https://github.com/modelcontextprotocol/rust-sdk/issues/815 (opens in a new tab)x_refsource_MISC
- https://github.com/modelcontextprotocol/rust-sdk/issues/822 (opens in a new tab)x_refsource_MISC
- https://github.com/modelcontextprotocol/rust-sdk/pull/764 (opens in a new tab)x_refsource_MISC
- https://github.com/modelcontextprotocol/rust-sdk/commit/8e22aa2de28df5a285eed87c11cd89bf15fa90d3 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-89vp-x53w-74fx (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-42559)Record last updated .