CVE-2026-123272

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{"bugzilla": {"description": "github.com/mark3labs/mcp-go: mcp-go: Unauthorized access via improper OAuth metadata validation", "id": "2567474", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2567474"}, "csaw": false, "cvss3": {"cvss3_base_score": "8.0", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N", "status": "draft"}, "cwe": "CWE-346", "details": ["A flaw was found in mcp-go. A malicious Model Context Protocol (MCP) server can declare arbitrary protected resources within its metadata due to improper validation in the OAuth metadata handler. This flaw allows an attacker to cause the authorization server to issue tokens scoped for unintended services, enabling unauthorized access when the attacker replays those tokens against the target resources."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability."}, "name": "CVE-2026-123272", "package_state": [{"cpe": "cpe:/a:redhat:connectivity_link:1", "fix_state": "Under investigation", "package_name": "rhcl-tech-preview/mcp-gateway-rhel9", "product_name": "Red Hat Connectivity Link 1"}, {"cpe": "cpe:/a:redhat:connectivity_link:1", "fix_state": "Under investigation", "package_name": "rhcl-tech-preview/mcp-gateway-rhel9-operator", "product_name": "Red Hat Connectivity Link 1"}, {"cpe": "cpe:/a:redhat:hummingbird:1", "fix_state": "Under investigation", "package_name": "tempo2.10", "product_name": "Red Hat Hardened Images"}, {"cpe": "cpe:/a:redhat:hummingbird:1", "fix_state": "Under investigation", "package_name": "tempo3.0", "product_name": "Red Hat Hardened Images"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Under investigation", "package_name": "rhoai/rhai-cli-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_distributed_tracing:3", "fix_state": "Under investigation", "package_name": "rhosdt/tempo-query-rhel9", "product_name": "Red Hat OpenShift distributed tracing 3"}, {"cpe": "cpe:/a:redhat:openshift_distributed_tracing:3", "fix_state": "Under investigation", "package_name": "rhosdt/tempo-rhel9", "product_name": "Red Hat OpenShift distributed tracing 3"}], "public_date": "2026-11-05T18:45:36Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-123272\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-123272\nhttps://github.com/mark3labs/mcp-go/blob/4cb0d2015f24b669726fd8e5e53fc8c6d3f57abf/client/transport/oauth.go#L799-L821\nhttps://github.com/mark3labs/mcp-go/commit/90d247ed8d45cbb7d71d9a95e112789b78760443\nhttps://github.com/mark3labs/mcp-go/pull/1053\nhttps://github.com/mark3labs/mcp-go/releases/tag/v1.2.1\nhttps://github.com/mark3labs/mcp-go/security/advisories/GHSA-xf6j-693p-wqxx\nhttps://www.vulncheck.com/advisories/mcp-go-before-1.2.1-origin-validation-error-via-unvalidated-well-known-protected-resource-metadata"], "statement": "This vulnerability is rated as Important because an adversarial Model Context Protocol (MCP) server can manipulate client authentication workflows to acquire authorization tokens for unrelated protected resources across trust boundaries. Successful exploitation requires an application or client session to establish a connection with an untrusted or rogue endpoint. In typical Red Hat deployments, clients connect exclusively to vetted, trusted infrastructure, significantly mitigating exposure to unsolicited server responses.", "threat_severity": "Important"}

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