SSRF (Server-Side Request Forgery) in mcp-from-openapi (CVE-2026-59973)
Summary
SSRF in mcp-from-openapi (CVE-2026-59973). Confidential information can be exposed externally. Exploitable via frontmcp. Mitigation: upgrade to 2.5.0 or later.
Original description
The description as published by the source.
Summary
The published fix for GHSA-v6ph-xcq9-qxxj / CVE-2026-39885 added a direct hostname denylist for OpenAPI external $ref dereferencing, but the latest patched dependency mcp-from-openapi 2.3.0 still makes backend-origin requests to loopback when the target is reached through hostname resolution, redirects, or IPv4-mapped IPv6 syntax.
FrontMCP latest release v1.2.1 and current main still call OpenAPIToolGenerator.fromURL() and OpenAPIToolGenerator.fromJSON() from mcp-from-openapi 2.3.0 when loading OpenAPI adapters. An attacker who can cause a hosted or multi-user FrontMCP deployment to load an untrusted OpenAPI spec can trigger requests from the server to localhost or private services during tool generation.
This is a latest-version bypass of the previous fix. A direct http://127.0.0.1 $ref control is now denied and produces zero canary hits, while semantically equivalent loopback targets still reach the canary.
Latest versions checked
frontmcpnpm latest: 1.2.1@frontmcp/adaptersnpm latest: 1.2.1mcp-from-openapinpm latest: 2.3.0- FrontMCP release tag: v1.2.1, commit db323976c66297d684a3e63bbfe1db6b310f2944
- FrontMCP current main checked: c15b79abe8c6a3cb71d4b7a3bafb8190730dc756
The release tag and current main both keep mcp-from-openapi 2.3.0 in package.json and libs/adapters/package.json, and both keep the OpenAPI adapter forwarding untrusted url, spec, and loadOptions.refResolution into OpenAPIToolGenerator.
##…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-59973 has been found in mcp-from-openapi.
Attackers can target a specific entry point like frontmcp over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 8.5/10.
What to do: upgrade mcp-from-openapi to 2.5.0 or later.
If unsure, ask your IT team or search "mcp-from-openapi CVE-2026-59973" on the vendor's site.
CVE-2026-59973 (mcp-from-openapi) — CWE-918 / CVSS v3 8.5
Attack vector: remote (network-reachable) / no user interaction
Attack surface: frontmcp / url / spec / loadOptions.refResolution
Patched: 2.5.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
SSRF (CWE-918) exists in mcp-from-openapi. Attackers reach the vulnerable code path via frontmcp.
Check the vendor advisory for the affected versions of mcp-from-openapi. Attack surface: frontmcp / url / spec / loadOptions.refResolution.
Severity: High (CVSS 8.5/10). Confidential information can be exposed externally.
Update to 2.5.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'mcp-from-openapi' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'mcp-from-openapi' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
mcp-from-openapiを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade mcp-from-openapi to 2.5.0ステージング環境で 2.5.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。