CVE-2026-81091

HIGHPre-NVD 8.68.6—
EchelonGraph scoreHIGH confidence

Score 8.6 from GitHub Security Advisory (severity: HIGH) published 2026-08-27. the CNA's CVSS baseline 8.6; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:vulncheck, epss, ghsa
Trending — 4 sources updated this week
8.6EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.6Exploit: None knownExposed: 0

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

The proxy middleware in mcp-use's inspector forwards requests to a destination the caller names. mountMcpProxy in libraries/typescript/packages/inspector/src/server/proxy/mcp-proxy.ts read the target from the X-Target-URL header or the __mcp_target parameter and proxied to it without inspecting the host, so loopback, link-local and private addresses were all accepted, as were names that resolve to them, and the validation was not reapplied to a redirect the destination returned. A caller could therefore make the server issue requests to addresses reachable only from the host it runs on and read the responses. The current code calls isSafeProxyTarget, which checks the resolved address against private, loopback and link-local ranges before proxying and bounds the number of redirects followed.

CVSS v3
8.6
EG Score
8.6(high)
EG Risk
54(Track)
EG Risk 54/100SSVC: Track

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
Severity86% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
27%
KEV
Not listed

Published

August 27, 2026

Last Modified

August 29, 2026

Advisory Details (2)

Auto-updated Aug 27, 2026
No patch confirmed yet.
generic

mcp-use Inspector Proxy Server-Side Request Forgery via Caller-Supplied Target URL | Advisories | VulnCheck

https://www.vulncheck.com/advisories/mcp-use-inspector-proxy-server-side-request-forgery-via-caller-supplied-target-url
generic

GitHub - mcp-use/mcp-use: The fullstack MCP framework to develop MCP Apps for ChatGPT / Claude & MCP Servers for AI Agents. · GitHub

https://github.com/mcp-use/mcp-use

Vendor Advisories for CVE-2026-81091(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 16× in last 7d / 16× 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.

  1. 2026-08-30 01:22 UTCEPSS rescore
  2. 2026-08-29 23:05 UTCGHSA enrichment
  3. 2026-08-29 11:59 UTCEG score recompute
  4. 2026-08-29 11:59 UTCGHSA enrichment
  5. 2026-08-29 05:51 UTCEG score recompute
  6. 2026-08-29 05:51 UTCGHSA enrichment
  7. 2026-08-28 21:42 UTCEPSS rescore
  8. 2026-08-28 18:47 UTCGHSA enrichment
  9. 2026-08-28 07:40 UTCGHSA enrichment
  10. 2026-08-27 20:27 UTCEG score recompute
  11. 2026-08-27 20:27 UTCGHSA enrichment
  12. 2026-08-27 20:18 UTCEG score recompute
  13. 2026-08-27 20:18 UTCGHSA enrichment
  14. 2026-08-27 17:27 UTCEG score recompute
  15. 2026-08-27 16:47 UTCEG score recompute
  16. 2026-08-27 16:43 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-81091?
CVE-2026-81091 is a high vulnerability published on August 27, 2026. The proxy middleware in mcp-use's inspector forwards requests to a destination the caller names. mountMcpProxy in libraries/typescript/packages/inspector/src/server/proxy/mcp-proxy.ts read the target from the X-Target-URL header or the mcp_target parameter and proxied to it without inspecting the…
When was CVE-2026-81091 disclosed?
CVE-2026-81091 was first published in the National Vulnerability Database on August 27, 2026, with the most recent update on August 29, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-81091 actively exploited?
CVE-2026-81091 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 73.2% of all scored CVEs.
What is the CVSS score of CVE-2026-81091?
CVE-2026-81091 has a CVSS v4.0 base score of 8.6 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-81091?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-81091, 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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