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CVE-2026-0621 Detail

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.


Metrics

NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

Nist CVSS score does not match with CNA score
CNA:  VulnCheck
CVSS-B 8.7 HIGH
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

References to Advisories, Solutions, and Tools

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URL Source(s) Tag(s)
https://github.com/modelcontextprotocol/typescript-sdk/issues/965 CISA-ADP, VulnCheck
https://www.vulncheck.com/advisories/mcp-typescript-sdk-uritemplate-exploded-array-pattern-redos VulnCheck

Weakness Enumeration

CWE-ID CWE Name Source
CWE-1333 Inefficient Regular Expression Complexity VulnCheck  

Change History

2 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2026-0621
NVD Published Date:
01/05/2026
NVD Last Modified:
01/08/2026
Source:
VulnCheck