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GHSA-8r9q-7v3j-jr4g
No affected components available
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
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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