CVE-2026-58196ToolHive: SSRF in remote MCP server authentication discovery (host-side, bypasses container isolation)
- 4.7MediumCVSS base score
- 0.43%Exploitation in 30 daysEPSS · top 62% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- YesPublic exploitsa reference or SSVC says so
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.
Public exploit
An exploit or proof of concept is public: anyone can try it against an unpatched system. A reference of the record is tagged as an exploit. CISA's SSVC rates its exploitation: a proof of concept is public.
Show the exploits1
References tagged exploit1 reference
- https://github.com/stacklok/toolhive/security/advisories/GHSA-pr64-jmmf-jp54 (opens in a new tab)x_refsource_CONFIRMexploit
Timeline
ID reserved
By GitHub_M
- 3 months later
· 3 months 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 | Medium4.7 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N |
| NVDNVD · Deferred | 3.1 | Medium4.7 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N |
- EPSS (exploitation in 30 days)
- 0.43% · top 62% of all CVEs (15 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 4.7.
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Gogithub.com/stacklok/toolhiveGHSA-pr64-jmmf-jp54 (opens in a new tab)
References
References3
- https://github.com/stacklok/toolhive/security/advisories/GHSA-pr64-jmmf-jp54 (opens in a new tab)x_refsource_CONFIRMexploit
- https://github.com/stacklok/toolhive/commit/4ea6afb9048ddec1d56875fa9e0da36d65c15966 (opens in a new tab)x_refsource_MISC
- https://github.com/stacklok/toolhive/releases/tag/v0.31.0 (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)
- EUVD EUVD-2026-78818 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-pr64-jmmf-jp54 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-58196)Record last updated .