{"id":"CVE-2026-45609","aliases":["GHSA-qjp4-4jvr-xqg3"],"url":"https://o3.security/vulnerability/CVE-2026-45609","summary":"mcp-security: Unvalidated URL Fetching (SSRF)","details":"### Summary\n\nThe mcp-security framework fails to implement the mandatory SSRF mitigations outlined in the Model Context Protocol (MCP) [security specifications](https://modelcontextprotocol.io/docs/tutorials/security/security_best_practices#mitigation-3). Specifically, it processes untrusted URLs for OAuth-related discovery and metadata without verifying if the targets are malicious or internal to the network.\n\nThis only affects installations with Dynamic Client Registration (DCR) enabled:\n\n```properties\nspring.ai.mcp.client.authorization.dynamic-client-registration.enabled=true\n```\n\nDCR does not validate URLs exposed by MCP Servers (protected resource metadata URL, authorization server URL) and Authorization Servers (all OAuth2 endpoints).\n\n### Workaround\n\nWhen users need to perform DCR, they may provide their own `McpOAuth2ClientManager`. Both `McpMetadataDiscoveryService` and `DynamicClientRegistrationService` are also affected, if used, users should provide their own subclasses.\n\nAlternatively, users can provide the default implementations of these classes with a `RestClient` that implements URL filtering through `ClientHttpRequestInterceptor`.","published":"2026-05-29T13:48:06.703Z","modified":"2026-08-12T03:51:37.336709165Z","cvss":{"score":7.2,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N"},"epss":{"score":0.00207,"percentile":0.10705,"asOf":"2026-08-24"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Maven","name":"org.springaicommunity:mcp-client-security","fixedVersion":"0.1.9"}],"fix":{"url":"https://github.com/spring-ai-community/mcp-security/pull/68","label":"spring-ai-community/mcp-security#68"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45609.json"},{"type":"ADVISORY","url":"https://github.com/spring-ai-community/mcp-security/security/advisories/GHSA-qjp4-4jvr-xqg3"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-45609"},{"type":"WEB","url":"https://github.com/spring-ai-community/mcp-security/pull/68"},{"type":"WEB","url":"https://github.com/spring-ai-community/mcp-security/commit/e6b67d8a67cd7acbee6e4c0741c385d62e3ed576"},{"type":"PACKAGE","url":"https://github.com/spring-ai-community/mcp-security"},{"type":"WEB","url":"https://github.com/spring-ai-community/mcp-security/releases/tag/v0.1.9"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:37.336709165Z"}}