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CVE-2026-81092— mcp-go before 0.56.0 Missing Host Header Validation Enables DNS Rebinding

Quick assessment

Affected
mark3labs mcp-go
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Mark III Labs MCP-Go是Mark III Labs组织的一个模型上下文协议的Go语言实现库。 Mark III Labs MCP-Go 0.56.0之前版本存在输入验证错误漏洞，该漏洞源于HTTP传输未检查Host标头，可能导致浏览器页面将受控名称指向回环地址并访问服务器，调用工具和读取资源。

CVSS 6.8 · Medium EPSS 0.22% · P12

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
mark3labs mcp-go < 0.56.0 affected
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I. Basic Information for CVE-2026-81092

Vulnerability Information
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Vulnerability Title
mcp-go before 0.56.0 Missing Host Header Validation Enables DNS Rebinding
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
源验证错误
Source: CVE Program / CVE List V5
Vulnerability Title
Mark III Labs MCP-Go 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mark III Labs MCP-Go是Mark III Labs组织的一个模型上下文协议的Go语言实现库。 Mark III Labs MCP-Go 0.56.0之前版本存在输入验证错误漏洞，该漏洞源于HTTP传输未检查Host标头，可能导致浏览器页面将受控名称指向回环地址并访问服务器，调用工具和读取资源。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
mark3labs mcp-go 0 ~ 0.56.0 -

II. Public POCs for CVE-2026-81092

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III. Intelligence Information for CVE-2026-81092

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Patches & Fixes for CVE-2026-81092 (1)

Vendor Advisories for CVE-2026-81092 (1)

Vendor Pages for CVE-2026-81092 (1)

IV. Related Vulnerabilities

Same product: mcp-go
Same vendor: mark3labs
Same weakness: CWE-346

V. Comments for CVE-2026-81092

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