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.
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-8r9q-7v3j-jr4g Anthropic's MCP TypeScript SDK has a ReDoS vulnerability
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Tue, 06 Jan 2026 14:30:00 +0000

Type Values Removed Values Added
First Time appeared Anthropic
Anthropic mcp Typescript Sdk
Vendors & Products Anthropic
Anthropic mcp Typescript Sdk

Tue, 06 Jan 2026 00:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Mon, 05 Jan 2026 21:00:00 +0000

Type Values Removed Values Added
Description 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.
Title MCP TypeScript SDK UriTemplate Exploded Array Pattern ReDoS
Weaknesses CWE-1333
References
Metrics cvssV4_0

{'score': 8.7, 'vector': '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'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-01-05T21:48:30.567Z

Reserved: 2026-01-05T19:41:59.356Z

Link: CVE-2026-0621

cve-icon Vulnrichment

Updated: 2026-01-05T21:07:49.707Z

cve-icon NVD

Status : Received

Published: 2026-01-05T21:16:14.533

Modified: 2026-01-05T22:15:54.387

Link: CVE-2026-0621

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-01-06T14:16:36Z

Weaknesses