CVE-2026-81092

MEDIUMPre-NVD 6.86.8—
EchelonGraph scoreHIGH confidence

Score 6.8 from GitHub Security Advisory (severity: HIGH) published 2026-08-27. the CNA's CVSS baseline 6.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:vulncheck, epss, ghsa
Trending — 4 sources updated this week
6.8EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.8Exploit: None knownExposed: 0

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

mcp-go accepted requests on its HTTP transports without checking the Host header. StreamableHTTPServer.ServeHTTP in server/streamable_http.go and SSEServer.ServeHTTP in server/sse.go served any request arriving over a loopback connection regardless of the host it named, and the SSE transport's cross-origin default allowed any origin. A page in a browser could therefore point a name it controlled at the loopback address and reach a server listening there, invoking tools and reading resources that the server exposed on the assumption that only local software could connect. No release before 0.56.0 validated the header on either transport; 0.56.0 adds server/http_localhost.go, which rejects a loopback-bound request carrying a host that is not a loopback name, and wires it into both transports.

CVSS v3
6.8
EG Score
6.8(high)
EG Risk
31(Track)
EG Risk 31/100SSVC: 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
Severity68% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
6%
KEV
Not listed

Published

August 27, 2026

Last Modified

August 29, 2026

Advisory Details (4)

Auto-updated Aug 27, 2026
Patch available. Sources: github_pr, github_release.
generic

mcp-go before 0.56.0 Missing Host Header Validation Enables DNS Rebinding | Advisories | VulnCheck

https://www.vulncheck.com/advisories/mcp-go-before-0.56.0-missing-host-header-validation-enables-dns-rebinding
github_release Patch Available

Release v0.56.0

Patch available: mark3labs/mcp-go v0.56.0

https://github.com/mark3labs/mcp-go/releases/tag/v0.56.0
github_pr Patch Available

feat(server): add automatic DNS rebinding protection for localhost

Patch available: mark3labs/mcp-go v0.56.0 (PR #921 merged 2026-07-08)

https://github.com/mark3labs/mcp-go/pull/921
generic

GitHub - mark3labs/mcp-go: A Go implementation of the Model Context Protocol (MCP), enabling seamless integration between LLM applications and external data sources and tools. · GitHub

https://github.com/mark3labs/mcp-go

Vendor Advisories for CVE-2026-81092(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 11× in last 7d / 11× 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 11:59 UTCEG score recompute
  3. 2026-08-29 11:59 UTCGHSA enrichment
  4. 2026-08-28 21:42 UTCEPSS rescore
  5. 2026-08-28 20:43 UTCEG score recompute
  6. 2026-08-28 20:43 UTCGHSA enrichment
  7. 2026-08-28 16:30 UTCEG score recompute
  8. 2026-08-28 16:29 UTCGHSA enrichment
  9. 2026-08-27 17:27 UTCEG score recompute
  10. 2026-08-27 16:47 UTCEG score recompute
  11. 2026-08-27 16:43 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-81092?
CVE-2026-81092 is a medium vulnerability published on August 27, 2026. mcp-go accepted requests on its HTTP transports without checking the Host header. StreamableHTTPServer.ServeHTTP in server/streamablehttp.go and SSEServer.ServeHTTP in server/sse.go served any request arriving over a loopback connection regardless of the host it named, and the SSE transport's…
When was CVE-2026-81092 disclosed?
CVE-2026-81092 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-2026-81092 actively exploited?
CVE-2026-81092 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 94.0% of all scored CVEs.
What is the CVSS score of CVE-2026-81092?
CVE-2026-81092 has a CVSS v4.0 base score of 6.8 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-81092?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-81092, 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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