Vulnerability Details CVE-2026-0621
Anthropic's MCP TypeScript SDK versions up to and including 1.25.1 contain a regular expression denial of service (ReDoS) vulnerability in the UriTemplate class when processing RFC 6570 exploded array patterns. The dynamically generated regular expression used during URI matching contains nested quantifiers that can trigger catastrophic backtracking on specially crafted inputs, resulting in excessive CPU consumption. An attacker can exploit this by supplying a malicious URI that causes the Node.js process to become unresponsive, leading to a denial of service.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 2.3%
CVSS Severity
CVSS v3 Score 7.5
References
Products affected by CVE-2026-0621
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cpe:2.3:a:lfprojects:mcp_typescript_sdk:*