{"cve":"CVE-2026-58196","nvd":{"published":"2026-09-15T16:17:16.817","modified":"2026-09-30T17:51:56.193","status":"Deferred","description":"ToolHive is a utility designed to simplify the deployment and management of Model Context Protocol (MCP) servers. Prior to 0.31.0, remote.Handler.Authenticate in pkg/auth/remote/handler.go invokes discovery.DetectAuthenticationFromServer in pkg/auth/discovery/discovery.go, whose host-side HTTP clients trust remote-server-controlled authentication discovery destinations, follow redirects without host or scheme restrictions, and do not consistently block private addresses. A malicious or compromised remote MCP server can place a resource_metadata URL in WWW-Authenticate for ParseWWWAuthenticate to extract, after which FetchResourceMetadata, OIDC issuer discovery, and well-known discovery can issue GET requests to link-local, RFC1918, or other internal services outside the server's container. The user connects to a server that the user intends to use, but the server controls the internal destination; this path does not depend on the separate NAT64 guard omission because the affected clients did not invoke IsPrivateIP, and it differs from the DCR resolver path that already refused redirects. The demonstrated primitive reaches internal-only HTTP services and reachability or error oracles, and can retrieve AWS metadata credentials where IMDSv1 accepts an unauthenticated GET, while IMDSv2 and GCP metadata prerequisites are not satisfied by the demonstrated request. This vulnerability is fixed in 0.31.0.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N","score":4.7},"cwes":["CWE-918"],"references":["https://github.com/stacklok/toolhive/commit/4ea6afb9048ddec1d56875fa9e0da36d65c15966","https://github.com/stacklok/toolhive/releases/tag/v0.31.0","https://github.com/stacklok/toolhive/security/advisories/GHSA-pr64-jmmf-jp54","https://github.com/stacklok/toolhive/security/advisories/GHSA-pr64-jmmf-jp54"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:53:43.293028046+00:00"},"epss":{"cve":"CVE-2026-58196","score":0.00429,"percentile":0.36889,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-pr64-jmmf-jp54","url":"https://osv.dev/vulnerability/GHSA-pr64-jmmf-jp54","summary":"ToolHive: SSRF in remote MCP server authentication discovery (host-side, bypasses container isolation)","modified":"2026-07-21T19:19:01.902714813Z","packages":[{"ecosystem":"Go","name":"github.com/stacklok/toolhive","purl":"pkg:golang/github.com/stacklok/toolhive","ranges":["<0.31.0"],"fixed":["0.31.0"]}]},{"id":"GO-2026-6002","url":"https://osv.dev/vulnerability/GO-2026-6002","summary":"ToolHive: SSRF in remote MCP server authentication discovery (host-side, bypasses container isolation) in github.com/stacklok/toolhive","modified":"2026-07-21T19:15:35.719157226Z","packages":[{"ecosystem":"Go","name":"github.com/stacklok/toolhive","purl":"pkg:golang/github.com/stacklok/toolhive","ranges":["<0.31.0"],"fixed":["0.31.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}