CVE-2026-77363: obsidian-tc Streamable HTTP transport permits cross-origin loopback vault access
obsidian-tc is a governed, agent-ready Model Context Protocol server for Obsidian vaults. Prior to 1.3.1, the Streamable HTTP transport does not validate the Host or Origin header or enable DNS-rebinding protection. When the documented loopback configuration uses auth.mode set to none, a malicious web page can send requests to the local MCP endpoint and receive unrestricted vault access through the http-local caller. Version 1.3.1 fixes the vulnerability by enabling host, origin, and DNS-rebinding validation.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
obsidian-tcto a version that resolves this vulnerability.Fixed in 1.3.1
Event History
Frequently Asked Questions
Which deployments are exposed to cross-origin access?
Deployments using the Streamable HTTP transport before version 1.3.1 are exposed when configured with the documented loopback setup and auth.mode set to none. In that configuration, a malicious web page can reach the local MCP endpoint through the http-local caller.
What does an attacker need to exploit this issue?
The attacker needs to convince a user to interact with a malicious web page. No authentication privileges are required when the affected endpoint uses auth.mode set to none.
What can an attacker access if exploitation succeeds?
The malicious page can send requests to the local MCP endpoint and obtain unrestricted access to the Obsidian vault through the http-local caller. The stated impact includes confidentiality, integrity, and availability.
What should be done if the service cannot be upgraded immediately?
The provided information identifies auth.mode set to none as part of the vulnerable documented loopback configuration. Avoiding that unauthenticated mode is the available configuration-based mitigation described by the advisory data; version 1.3.1 is the stated fix.