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.

References

Affected packages

Git / github.com/modelcontextprotocol/typescript-sdk

Affected ranges

Type

GIT

Repo

https://github.com/modelcontextprotocol/typescript-sdk

Events

Introduced

Last affected

384311b9b8452017f5f81819c133dc45c667cfa4

Database specific

{
    "versions": [
        {
            "introduced": "0"
        },
        {
            "last_affected": "1.25.1"
        }
    ]
}

Affected versions

0.*

0.1.0

0.15.1

0.2.0

0.3.0

0.3.1

0.3.2

0.4.0

0.5.0

0.6.0

0.6.1

0.7.0

1.*

1.0.0

1.0.1

1.0.2

1.0.3

1.0.4

1.1.0

1.1.1

1.10.0

1.10.1

1.10.2

1.11.0

1.11.1

1.11.2

1.11.3

1.11.4

1.12.0

1.12.1

1.12.2

1.12.3

1.13.0

1.13.1

1.13.2

1.13.3

1.14.0

1.15.0

1.15.1

1.16.0

1.17.0

1.17.1

1.17.2

1.17.3

1.17.4

1.17.5

1.18.0

1.18.1

1.18.2

1.19.0

1.2.0

1.20.0

1.20.1

1.20.2

1.21.0

1.21.1

1.22.0

1.23.0

1.23.0-beta.0

1.24.0

1.24.1

1.24.2

1.24.3

1.25.0

1.25.1

1.3.0

1.3.1

1.3.2

1.4.0

1.4.1

1.5.0

1.6.0

1.6.1

1.7.0

1.8.0

1.9.0

Database specific

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-0621.json"