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archive/Patch now/AIR-2026-0425
closedclosed 5 Jan 2026Patch now2 Disclosed vulnerabilityAI

CVE-2026-0621: Anthropic's MCP TypeScript SDK has a ReDoS vulnerability

MCP TypeScript SDK

A regular expression denial of service vulnerability exists in the UriTemplate class of Anthropic's Model Context Protocol TypeScript SDK. Crafted requests can cause 100% CPU utilization and server crashes.

disclosed CVENo confirmed exploitation, so this record is tracked as a disclosed vulnerability and not counted as an incident. It moves into the counts if CISA or the vendor confirms exploitation. Why

CVSS
8.7
EPSS
<0.01 · top 62% · 2026-11-13
EPSS scores by FIRST
fix status
Fix status unknown
first report
5 Jan 2026
last update
5 Jan 2026
CVE ids
CVE-2026-0621other records

Timeline · 1

  1. 5 Jan 2026CVE-2026-0621: Anthropic's MCP TypeScript SDK has a ReDoS vulnerability

Sources · 1

Advisories and databases

  1. 2026-01-05
    CVE-2026-0621: Anthropic's MCP TypeScript SDK has a ReDoS vulnerability
    GitHub Advisory Database · github.com/advisories/GHSA-8r9q-7v3j-jr4g

Titles and links belong to their publishers. The summary above is written by gcdRadar in its own words; data is CC BY-SA 4.0.

Classification

lane
Patch now
AI role
Attack on AI
categories
Infrastructure vulnerability
severity
2 · Disclosed vulnerability
fix status
Fix status unknown
targets
Framework / tooling
owasp llm top 10
LLM03:2025 Supply Chain
mitre atlas
no technique for these categories
tags
mcpanthropicredos
dates
happened 5 Jan 2026 · first reported 5 Jan 2026
origin
GitHub Advisory Database
Vulnerability record from NVD / the GitHub Advisory Database. This product uses the NVD API but is not endorsed or certified by the NVD.
record
confidence 0.95 · created 2026-10-18 07:00Z · updated 2026-10-18 07:00Z

Lane, AI role, categories and severity come from the classifier; the OWASP and ATLAS rows are derived from the categories. How these are assigned

Copy a brief

This record as a short Markdown brief, for a ticket, a chat or a coding agent.

the brief as text
# CVE-2026-0621: Anthropic's MCP TypeScript SDK has a ReDoS vulnerability

https://gcdradar.vercel.app/incidents/cve-2026-0621-anthropic-s-mcp-typescript-sdk-has-a-redos-vul · AIR-2026-0425 · closed 2026-01-05

- Lane: Patch now
- Severity: 2 (Disclosed vulnerability)
- Fix status: Fix status unknown
- First reported: 2026-01-05
- AI role: Attack on AI
- Products: MCP TypeScript SDK
- CVE ids: CVE-2026-0621
- CVSS: 8.7

## Summary

A regular expression denial of service vulnerability exists in the UriTemplate class of Anthropic's Model Context Protocol TypeScript SDK. Crafted requests can cause 100% CPU utilization and server crashes.

## What to do

No action recorded; read the sources below and the vendor's advisory.

## Latest updates

- 2026-01-05: CVE-2026-0621: Anthropic's MCP TypeScript SDK has a ReDoS vulnerability (https://github.com/advisories/GHSA-8r9q-7v3j-jr4g)

## Sources

- 2026-01-05 GitHub Advisory Database: CVE-2026-0621: Anthropic's MCP TypeScript SDK has a ReDoS vulnerability https://github.com/advisories/GHSA-8r9q-7v3j-jr4g

Verify against the vendor's advisory before changing production. Data CC BY-SA 4.0, https://gcdradar.vercel.app.

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