CVE-2026-32871

CRITICALNVD 10.010.0—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 10.0 under NVD CVSS v3. EPSS exploit probability: 1.0%, top 40% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Elevated
10.0EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 10.0Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

FastMCP is a Pythonic way to build MCP servers and clients. Prior to version 3.2.0, the OpenAPIProvider in FastMCP exposes internal APIs to MCP clients by parsing OpenAPI specifications. The RequestDirector class is responsible for constructing HTTP requests to the backend service. A vulnerability exists in the _build_url() method. When an OpenAPI operation defines path parameters (e.g., /api/v1/users/{user_id}), the system directly substitutes parameter values into the URL template string without URL-encoding. Subsequently, urllib.parse.urljoin() resolves the final URL. Since urljoin() interprets ../ sequences as directory traversal, an attacker controlling a path parameter can perform path traversal attacks to escape the intended API prefix and access arbitrary backend endpoints. This results in authenticated SSRF, as requests are sent with the authorization headers configured in the MCP provider. This issue has been patched in version 3.2.0.

CVSS v3
10.0
EG Score
10.0(medium)
EG Risk
76(Attend)
EG Risk 76/100SSVC: Attend

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity100% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
1%
EPSS %ILE
56%
KEV
Not listed

Published

April 2, 2026

Last Modified

July 15, 2026

Advisory Details (8)

Auto-updated Jul 22, 2026
🔬 Proof of concept available. Patch available. Sources: github_pr, github_release, github, redhat, github_commit.
redhat Patch Available
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-32871.json
github Patch Available🟡 PoC Available

SSRF & Path Traversal Vulnerability in FastMCP OpenAPI Provider · Advisory · PrefectHQ/fastmcp · GitHub

https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-vv7q-7jx5-f767
redhat

2454434 – (CVE-2026-32871) CVE-2026-32871 fastmcp: FastMCP: Authenticated Server-Side Request Forgery via path traversal in OpenAPI path parameters

https://bugzilla.redhat.com/show_bug.cgi?id=2454434
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/CVE-2026-32871
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:36350
github_release Patch Available

v3.2.0: Show Don't Tool

Patch available: PrefectHQ/fastmcp v3.2.0

https://github.com/PrefectHQ/fastmcp/releases/tag/v3.2.0
github_pr Patch Available

fix: URL-encode path params to prevent SSRF/path traversal (GHSA-vv7q-7jx5-f767)

Patch available: PrefectHQ/fastmcp v3.2.0 (PR #3507 merged 2026-03-15)

https://github.com/PrefectHQ/fastmcp/pull/3507
github_commit Patch Available

commit 40bdfb6b1de0 (PrefectHQ/fastmcp)

Patch available: PrefectHQ/fastmcp v3.2.0 (contains commit 40bdfb6b1de0)

https://github.com/PrefectHQ/fastmcp/commit/40bdfb6b1de0ce30609ee9ba5bb95ecd04a9fb71

Vendor Advisories for CVE-2026-32871(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
fastmcp0.1.0 ... 3.1.1 (91 versions)3.2.0—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 52× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 119 total refreshes for this CVE.

  1. 2026-07-27 14:13 UTCEPSS rescore
  2. 2026-07-26 14:54 UTCEPSS rescore
  3. 2026-07-26 14:54 UTCEPSS rescore
  4. 2026-07-25 14:18 UTCEPSS rescore
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  8. 2026-07-23 14:18 UTCEPSS rescore
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  10. 2026-07-23 03:09 UTCEG score recompute
  11. 2026-07-22 14:08 UTCEPSS rescore
  12. 2026-07-21 15:24 UTCEPSS rescore
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  20. 2026-07-17 12:29 UTCOSV refresh
  21. 2026-07-16 17:03 UTCEPSS rescore
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  23. 2026-07-15 16:57 UTCEPSS rescore
  24. 2026-07-15 16:57 UTCEPSS rescore
  25. 2026-07-15 02:23 UTCNVD updateCVSS v3 → 10 · severity → CRITICAL
Show 75 more
  1. 2026-07-15 02:00 UTCEPSS rescore
  2. 2026-07-15 02:00 UTCEPSS rescore
  3. 2026-07-15 01:21 UTCMITRE cvelistV5CVSS v3 → 8.5 · severity → HIGH
  4. 2026-07-13 22:30 UTCEPSS rescore
  5. 2026-07-13 06:13 UTCEPSS rescore
  6. 2026-07-13 06:13 UTCEPSS rescore
  7. 2026-07-12 05:46 UTCEPSS rescore
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  9. 2026-07-09 19:10 UTCEPSS rescore
  10. 2026-07-08 15:15 UTCEPSS rescore
  11. 2026-07-08 14:36 UTCNVD updateCVSS v3 → 10 · severity → CRITICAL
  12. 2026-07-08 12:47 UTCMITRE cvelistV5CVSS v3 → 8.5 · severity → HIGH
  13. 2026-07-07 13:46 UTCEPSS rescore
  14. 2026-07-06 16:27 UTCEPSS rescore
  15. 2026-07-06 16:27 UTCEPSS rescore
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  24. 2026-06-28 14:07 UTCEPSS rescore
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  26. 2026-06-28 04:56 UTCEPSS rescore
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  29. 2026-06-25 13:49 UTCEPSS rescore
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  31. 2026-06-24 14:05 UTCEPSS rescore
  32. 2026-06-23 21:33 UTCEPSS rescore
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  34. 2026-06-22 14:25 UTCEPSS rescore
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  36. 2026-06-21 14:56 UTCEPSS rescore
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  38. 2026-06-21 01:59 UTCEPSS rescore
  39. 2026-06-19 19:25 UTCEPSS rescore
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  41. 2026-06-18 17:52 UTCEPSS rescore
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  44. 2026-06-16 17:52 UTCEPSS rescore
  45. 2026-06-15 17:49 UTCEPSS rescore
  46. 2026-06-14 23:18 UTCEPSS rescore
  47. 2026-06-13 23:00 UTCEPSS rescore
  48. 2026-06-12 23:12 UTCEPSS rescore
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  50. 2026-06-11 14:00 UTCEPSS rescore
  51. 2026-06-10 22:18 UTCEPSS rescore
  52. 2026-06-10 13:22 UTCEPSS rescore
  53. 2026-06-08 14:17 UTCEPSS rescore
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  55. 2026-06-07 15:25 UTCEPSS rescore
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  58. 2026-06-06 13:47 UTCEPSS rescore
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  60. 2026-06-05 22:47 UTCEPSS rescore
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  64. 2026-06-04 13:12 UTCEPSS rescore
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  66. 2026-06-02 20:13 UTCEPSS rescore
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  70. 2026-05-31 22:30 UTCEPSS rescore
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  74. 2026-05-31 00:16 UTCEPSS rescore
  75. 2026-05-29 13:44 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2026-32871?
CVE-2026-32871 is a critical vulnerability published on April 2, 2026. FastMCP is a Pythonic way to build MCP servers and clients. Prior to version 3.2.0, the OpenAPIProvider in FastMCP exposes internal APIs to MCP clients by parsing OpenAPI specifications. The RequestDirector class is responsible for constructing HTTP requests to the backend service. A vulnerability…
When was CVE-2026-32871 disclosed?
CVE-2026-32871 was first published in the National Vulnerability Database on April 2, 2026, with the most recent update on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-32871 actively exploited?
CVE-2026-32871 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 43.7% of all scored CVEs.
What is the CVSS score of CVE-2026-32871?
CVE-2026-32871 has a CVSS v3 base score of 10.0 (NVD).
How do I remediate CVE-2026-32871?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-32871, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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