Answer in brief
CVE-2026-0621 records a High severity (CVSS 8.7) vulnerability in MCP TypeScript SDK UriTemplate Exploded Array Pattern ReDoS. The current sources do not mark it as known exploited. The current feed maps Anthropic/MCP TypeScript SDK (generic), @modelcontextprotocol/sdk (npm). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Anthropic/MCP TypeScript SDK (generic), @modelcontextprotocol/sdk (npm). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Anthropic/MCP TypeScript SDKgeneric | >=0 <=1.25.1 | Not reported |
| @modelcontextprotocol/sdknpm | >=1.3.0,<1.25.2 | 1.25.2 |
Published upstream
Jan 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 8, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 15, 2026
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.
Quoted source text, attributed separately from HOL analysis.