{"id":"GHSA-8r9q-7v3j-jr4g","summary":"Anthropic's MCP TypeScript SDK has a ReDoS vulnerability","details":"### Impact\n\nA ReDoS vulnerability in the `UriTemplate` class allows attackers to cause denial of service. The `partToRegExp()` function generates a regex pattern with nested quantifiers (`([^/]+(?:,[^/]+)*)`) for exploded template variables (e.g., `{/id*}`, `{?tags*}`), causing catastrophic backtracking on malicious input.\n\n**Who is affected:** MCP servers that register resource templates with exploded array patterns and accept requests from untrusted clients.\n\n**Attack result:** An attacker sends a crafted URI via `resources/read` request, causing 100% CPU utilization, server hang/crash, and denial of service for all clients.\n\n### Affected Versions\n\nAll versions of `@modelcontextprotocol/sdk` prior to the patched release.\n\n### Patches\n\nv1.25.2 contains b392f02ffcf37c088dbd114fedf25026ec3913d3 the fix modifies the regex pattern to prevent backtracking.\n\n### Workarounds\n\n- Avoid using exploded patterns (`{/id*}`, `{?tags*}`) in resource templates\n- Implement request timeouts and rate limiting\n- Validate URIs before processing to reject suspicious patterns","aliases":["CVE-2026-0621"],"modified":"2026-07-17T21:06:39.800088312Z","published":"2026-01-05T21:30:33Z","database_specific":{"cwe_ids":["CWE-1333"],"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-01-06T21:20:37Z","nvd_published_at":"2026-01-05T21:16:14Z"},"references":[{"type":"WEB","url":"https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-cqwc-fm46-7fff"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-0621"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/typescript-sdk/issues/965"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/typescript-sdk/commit/7f0cf730"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/typescript-sdk/commit/b392f02ffcf37c088dbd114fedf25026ec3913d3"},{"type":"PACKAGE","url":"https://github.com/modelcontextprotocol/typescript-sdk"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/v1.25.2"},{"type":"WEB","url":"https://www.vulncheck.com/advisories/mcp-typescript-sdk-uritemplate-exploded-array-pattern-redos"}],"affected":[{"package":{"name":"@modelcontextprotocol/sdk","ecosystem":"npm","purl":"pkg:npm/%40modelcontextprotocol/sdk"},"ranges":[{"type":"SEMVER","events":[{"introduced":"1.3.0"},{"fixed":"1.25.2"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/01/GHSA-8r9q-7v3j-jr4g/GHSA-8r9q-7v3j-jr4g.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"}]}