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2 vulnerabilities by mark3labs
CVE-2026-81092 (GCVE-0-2026-81092)
Vulnerability from nvd – Published: 2026-08-27 14:50 – Updated: 2026-08-29 11:48
VLAI
EPSS
VEX
Title
mcp-go before 0.56.0 Missing Host Header Validation Enables DNS Rebinding
Summary
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.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-27 18:24 UTC
CWE
- CWE-346 - Origin Validation Error
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/mark3labs/mcp-go | product |
| https://github.com/mark3labs/mcp-go/pull/921 | issue-trackingpatch |
| https://github.com/mark3labs/mcp-go/releases/tag/… | release-notes |
| https://www.vulncheck.com/advisories/mcp-go-befor… | third-party-advisory |
Date Public
2026-08-26 00:00
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CVE-2026-81092 (GCVE-0-2026-81092)
Vulnerability from cvelistv5 – Published: 2026-08-27 14:50 – Updated: 2026-08-29 11:48
VLAI
EPSS
VEX
Title
mcp-go before 0.56.0 Missing Host Header Validation Enables DNS Rebinding
Summary
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.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-27 18:24 UTC
CWE
- CWE-346 - Origin Validation Error
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/mark3labs/mcp-go | product |
| https://github.com/mark3labs/mcp-go/pull/921 | issue-trackingpatch |
| https://github.com/mark3labs/mcp-go/releases/tag/… | release-notes |
| https://www.vulncheck.com/advisories/mcp-go-befor… | third-party-advisory |
Date Public
2026-08-26 00:00
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