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CVE

GHSA-8r9q-7v3j-jr4g

Anthropic's MCP TypeScript SDK has a ReDoS vulnerability
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CVE

GHSA-8r9q-7v3j-jr4g

Anthropic's MCP TypeScript SDK has a ReDoS vulnerability

Impact

A ReDoS vulnerability in the UriTemplate class allows attackers to cause denial of service. The partToRegExp() function generates a regex pattern with nested quantifiers (([^/]+(?:,[^/]+)*)) for exploded template variables (e.g., {/id*}, {?tags*}), causing catastrophic backtracking on malicious input.

Who is affected: MCP servers that register resource templates with exploded array patterns and accept requests from untrusted clients.

Attack result: An attacker sends a crafted URI via resources/read request, causing 100% CPU utilization, server hang/crash, and denial of service for all clients.

Affected Versions

All versions of @modelcontextprotocol/sdk prior to the patched release.

Patches

v1.25.2 contains b392f02ffcf37c088dbd114fedf25026ec3913d3 the fix modifies the regex pattern to prevent backtracking.

Workarounds

  • Avoid using exploded patterns ({/id*}, {?tags*}) in resource templates
  • Implement request timeouts and rate limiting
  • Validate URIs before processing to reject suspicious patterns

Package Versions Affected

Package Version
patch Availability
No items found.

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CVSS Version

Severity
Base Score
CVSS Version
Score Vector
C
H
U
8.7
-
4.0
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
C
H
U
0
-
C
H
U
-

Related Resources

No items found.

References

https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-cqwc-fm46-7fff, https://nvd.nist.gov/vuln/detail/CVE-2026-0621, https://github.com/modelcontextprotocol/typescript-sdk/issues/965, https://github.com/modelcontextprotocol/typescript-sdk/commit/b392f02ffcf37c088dbd114fedf25026ec3913d3, https://github.com/modelcontextprotocol/typescript-sdk, https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/v1.25.2, https://www.vulncheck.com/advisories/mcp-typescript-sdk-uritemplate-exploded-array-pattern-redos

Severity

0

CVSS Score
0
10

Basic Information

Ecosystem
Base CVSS
0
EPSS Probability
0.00055%
EPSS Percentile
0.1754%
Introduced Version
0
Fix Available
1.25.2

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