CVE-2026-81100: Origin Validation Error in timescale tiger-gh-mcp-server

The tiger-gh-mcp-server component of timescale started its MCP HTTP transport without enabling the host allow-list feature provided by the underlying SDK. Specifically, the shared httpServerFactory helper used in src/httpServer.ts did not set the DNS-rebinding-protection option, causing the transport to accept HTTP requests regardless of the host header. This allowed a locally reachable GitHub MCP endpoint to be manipulated from a visitor's browser if the attacker controlled the host name used in the request. The fix involved explicitly passing the DNS-rebinding-protection option along with a dependency update; the dependency update alone was insufficient to close the vulnerability. No official release brackets the fix, so the affected boundary is the commit before the fix was applied.

An attacker can exploit this vulnerability to perform DNS rebinding attacks against the locally reachable GitHub MCP endpoint, potentially allowing unauthorized control or manipulation of the endpoint from a visitor's browser. This could lead to unauthorized actions or data exposure within the local network context of the server. The vulnerability has a CVSS 4.0 score of 7.6, indicating high severity with network attack vector, low attack complexity, and requiring user interaction and partial privileges.

No official release currently contains the fix, so users should apply the fix by explicitly enabling the DNS-rebinding-protection option in the httpServerFactory helper as described in the fix commit. The dependency update alone does not mitigate the issue. Monitor the vendor repository for an official release including this fix. Until then, consider applying the fix manually or restricting access to the MCP HTTP transport to trusted hosts.