{"id":"CVE-2026-81092","aliases":["EUVD-2026-67147","GHSA-8g5x-gj7x-mxgm","RHSA-2026:54874","RHSA-2026:62527","RHSA-2026:62537","SUSE-SU-2026:23496-1","SUSE-SU-2026:23636-1","openSUSE-SU-2026:11670-1","openSUSE-SU-2026:21771-1"],"status":"published","title":"mcp-go before 0.56.0 Missing Host Header Validation Enables DNS Rebinding","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.","severity":{"version":"4.0","score":7.6,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00223,"percentile":0.13032,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-346"],"published":"2026-08-27T14:50:33Z","modified":"2026-10-28T02:30:56Z","fixes":[{"ecosystem":"Red Hat:hummingbird:1","package":"tempo3.0","fixed_in":["0:3.0.3-0.1.hum1"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Red Hat:hummingbird:1","package":"tempo3.0","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0:3.0.3-0.1.hum1"}]}]},{"source":"osv","ecosystem":"Red Hat:hummingbird:1","package":"tempo2.10","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0:2.10.8-0.2.hum1"}]}],"bundled":2},{"source":"osv","ecosystem":"Red Hat:hummingbird:1","package":"tempo3.0","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0:3.0.3-0.2.hum1"}]}],"bundled":2},{"source":"osv","ecosystem":"SUSE:Linux Micro 6.2","package":"mcphost","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.34.0-160000.4.1"}]}],"bundled":2},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Server 16.0","package":"mcphost","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.34.0-160000.4.1"}]}],"bundled":2},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Server for SAP applications 16.0","package":"mcphost","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.34.0-160000.4.1"}]}],"bundled":2},{"source":"osv","ecosystem":"openSUSE:Tumbleweed","package":"mcphost","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.34.0-10.1"}]}],"bundled":2},{"source":"osv","ecosystem":"openSUSE:Leap 16.0","package":"mcphost","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.34.0-160000.4.1"}]}],"bundled":2}],"products":[{"vendor":"mark3labs","product":"mcp-go"}],"references":[{"url":"https://github.com/mark3labs/mcp-go","tags":["product","package","article"]},{"url":"https://github.com/mark3labs/mcp-go/pull/921","tags":["issue-tracking","patch","fix","article"]},{"url":"https://github.com/mark3labs/mcp-go/releases/tag/v0.56.0","tags":["release-notes","advisory","article"]},{"url":"https://www.vulncheck.com/advisories/mcp-go-before-0.56.0-missing-host-header-validation-enables-dns-rebinding","tags":["third-party-advisory","advisory","article"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-81092","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-8g5x-gj7x-mxgm"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81092.json","tags":["advisory"]},{"url":"https://access.redhat.com/errata/RHSA-2026:54874","tags":["advisory"]},{"url":"https://images.redhat.com/","tags":["article"]},{"url":"https://access.redhat.com/security/cve/CVE-2026-81092","tags":["report"]},{"url":"https://access.redhat.com/security/updates/classification/","tags":["article"]},{"url":"https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_54874.json","tags":["advisory"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2525106","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-81092","tags":["advisory"]},{"url":"https://access.redhat.com/errata/RHSA-2026:62527","tags":["advisory"]},{"url":"https://access.redhat.com/security/cve/CVE-2026-10601","tags":["report"]},{"url":"https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_62527.json","tags":["advisory"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2491359","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-10601","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-10601","tags":["advisory"]},{"url":"https://grafana.com/security/security-advisories/cve-2026-10601","tags":["article"]},{"url":"https://access.redhat.com/errata/RHSA-2026:62537","tags":["advisory"]},{"url":"https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_62537.json","tags":["advisory"]},{"url":"https://www.suse.com/support/update/announcement/2026/suse-su-202623496-1/","tags":["advisory"]},{"url":"https://bugzilla.suse.com/1276612","tags":["report"]},{"url":"https://bugzilla.suse.com/1278013","tags":["report"]},{"url":"https://www.suse.com/security/cve/CVE-2026-41178","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-81092","tags":["web"]},{"url":"https://www.suse.com/support/update/announcement/2026/suse-su-202623636-1/","tags":["advisory"]},{"url":"","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-81092","title":"mcp-go before 0.56.0 Missing Host Header Validation Enables DNS Rebinding","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.","status":"published","published":"2026-08-27T14:50:33.286Z","modified":"2026-08-29T11:48:08.125Z","cvss":[{"version":"4.0","score":7.6,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high","assessor":"cna"},{"version":"3.1","score":6.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-346"],"updated_at":"2026-11-02T13:36:18.075535Z"}],"euvd":[{"id":"EUVD-2026-67147","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.","status":"published","published":"2026-08-27T14:50:33Z","modified":"2026-08-29T11:48:08Z","cvss":[{"version":"4.0","score":7.6,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"}],"updated_at":"2026-11-02T18:01:21.947009Z"}],"ghsa":[{"id":"GHSA-8g5x-gj7x-mxgm","title":"mcp-go accepted requests on its HTTP transports without checking the Host header....","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.","status":"published","published":"2026-08-27T18:32:25Z","modified":"2026-08-27T18:32:30Z","cvss":[{"version":"4.0","score":7.6,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high"},{"version":"3.1","score":6.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"medium"}],"cwes":["CWE-346"],"updated_at":"2026-11-02T15:11:05.100142Z"}],"nvd":[{"id":"CVE-2026-81092","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.","status":"published","published":"2026-08-27T17:20:51.337Z","modified":"2026-09-23T17:17:43.41Z","cvss":[{"version":"4.0","score":7.6,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high","assessor":"secondary"},{"version":"3.1","score":6.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-346"],"updated_at":"2026-11-02T14:12:42.035353Z"}],"osv":[{"id":"CVE-2026-81092","title":"mcp-go before 0.56.0 Missing Host Header Validation Enables DNS Rebinding","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.","status":"published","published":"2026-08-27T14:50:33.286Z","modified":"2026-10-28T02:30:56.644497112Z","cvss":[{"version":"4.0","score":7.6,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-346"],"updated_at":"2026-11-02T15:45:18.131258Z"},{"id":"RHSA-2026:54874","title":"Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update","status":"published","published":"2026-09-05T10:15:46Z","modified":"2026-09-09T10:17:38Z","cvss":[{"version":"3.1","score":6.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"medium"}],"updated_at":"2026-11-02T15:53:21.457353Z"},{"id":"RHSA-2026:62527","title":"Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update","status":"published","published":"2026-09-05T10:17:18Z","modified":"2026-09-22T10:42:44.877267643Z","cvss":[{"version":"3.1","score":6.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"medium"}],"updated_at":"2026-11-02T15:53:21.91255Z"},{"id":"RHSA-2026:62537","title":"Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update","status":"published","published":"2026-09-06T10:18:08Z","modified":"2026-09-22T10:42:43.636021761Z","cvss":[{"version":"3.1","score":6.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"medium"}],"updated_at":"2026-11-02T15:53:21.91255Z"},{"id":"openSUSE-SU-2026:11670-1","title":"mcphost-0.34.0-10.1 on GA media","description":"These are all security issues fixed in the mcphost-0.34.0-10.1 package on the GA media of openSUSE Tumbleweed.","status":"published","published":"2026-09-02T00:00:00Z","modified":"2026-09-03T10:00:08.663871546Z","updated_at":"2026-11-02T16:58:39.516824Z"},{"id":"openSUSE-SU-2026:21771-1","title":"Security update for mcphost","description":"This update for mcphost fixes the following issues:\n\n- CVE-2026-41178: go.opentelemetry.io/otel/baggage: no rejection of raw-length headers in baggage parsing allows for DoS\n  via oversized inputs (bsc#1276612).\n- CVE-2026-81092: github.com/mark3labs/mcp-go/server: requests accepted in HTTP transports without Host header checks\n  can lead to tool usage and resource exposure in target server (bsc#1278013).\n\nChanges for mcphost:\n\n- Update github.com/mark3labs/mcp-go/server to v0.56.0.\n- Update go.opentelemetry.io/otel to 1.44.0.\n","status":"published","published":"2026-09-06T16:48:02Z","modified":"2026-09-09T18:23:14.994239561Z","updated_at":"2026-11-02T16:58:42.426393Z"},{"id":"SUSE-SU-2026:23496-1","title":"Security update for mcphost","description":"This update for mcphost fixes the following issues:\n\n- CVE-2026-41178: go.opentelemetry.io/otel/baggage: no rejection of raw-length headers in baggage parsing allows for DoS\n  via oversized inputs (bsc#1276612).\n- CVE-2026-81092: github.com/mark3labs/mcp-go/server: requests accepted in HTTP transports without Host header checks\n  can lead to tool usage and resource exposure in target server (bsc#1278013).\n\nChanges for mcphost:\n\n- Update github.com/mark3labs/mcp-go/server to v0.56.0.\n- Update go.opentelemetry.io/otel to 1.44.0.\n","status":"published","published":"2026-09-06T16:47:47Z","modified":"2026-09-14T18:23:15.683011166Z","updated_at":"2026-11-02T15:54:03.991985Z"},{"id":"SUSE-SU-2026:23636-1","title":"Security update for mcphost","description":"This update for mcphost fixes the following issues:\n\n- CVE-2026-41178: go.opentelemetry.io/otel/baggage: no rejection of raw-length headers in baggage parsing allows for DoS\n  via oversized inputs (bsc#1276612).\n- CVE-2026-81092: github.com/mark3labs/mcp-go/server: requests accepted in HTTP transports without Host header checks\n  can lead to tool usage and resource exposure in target server (bsc#1278013).\n\nChanges for mcphost:\n\n- Update github.com/mark3labs/mcp-go/server to v0.56.0.\n- Update go.opentelemetry.io/otel to 1.44.0.\n","status":"published","published":"2026-09-06T16:47:47Z","modified":"2026-09-29T18:23:10.39723393Z","updated_at":"2026-11-02T15:54:03.991985Z"}]}}