Obsidian-TC 9.9 Flaw Exposes All Vaults in Versions Before 1.3.1

Security teams using The-40-Thieves obsidian-tc must verify their deployment versions immediately. The NVD record for CVE-2026-77366 identifies a critical vulnerability in the Model Context Protocol server. Environments running software prior to version 1.3.1 are exposed to a complete breakdown of data isolation between vaults. This exposure allows unauthorized access to sensitive note structures and content.

How does the vulnerability bypass access controls?

The obsidian-tc server fails to validate the vault identifier provided by the caller. According to the NVD description, the tool dispatch mechanism does not compare the input.vault value against the vault bound to the caller. Additionally, the JSON Web Token used for authentication lacks a specific vault claim. This design flaw means that any valid token can select a different configured vault.

What actions can an attacker perform?

An adversary with a valid token can read, write, or delete contents in any vault. The folder access-control list is shared globally across the system. This global sharing allows the attacker to manipulate data outside their intended scope. The vulnerability is categorized under CWE-639 and CWE-863. These weaknesses highlight the failure in authorization checks and resource management.

Which versions are affected and fixed?

The vulnerability exists in all versions of obsidian-tc prior to 1.3.1. The vendor released version 1.3.1 to address this security gap. The update fixes the vulnerability by binding tokens and request context to a specific vault. It also rejects mismatched input.vault values before performing scope checks. Teams should confirm they are running version 1.3.1 or later.

Why is this a high priority for defenders?

The CVSS score of 9.9 indicates a critical severity level. This rating reflects the ease of exploitation and the impact on confidentiality and integrity. Since any valid token can be abused, the attack surface is large. Defenders cannot rely on token validity alone to ensure security. The lack of vault-specific claims in the token makes isolation impossible in older versions.

Detection notes

Teams usually monitor for unusual file access patterns in log files. Look for requests where the token owner does not match the vault being accessed. Check for rapid reading or deletion of files across multiple directories. Verify that access-control lists are not being bypassed by unexpected users. Review server logs for mismatched input values during tool dispatch. Containment moves should include restricting network access to the server. Disable remote tool execution if immediate patching is not possible. Monitor for new tokens being generated or used.

What to do and how to stay safe: obsidian-tc

• Check your obsidian-tc version and upgrade to 1.3.1 if you are running an earlier release.
• Review authentication logs to identify any tokens that accessed vaults they should not have.
• Verify that your folder access-control lists are not shared globally in your configuration.
• Monitor for unusual read or write activity in vaults that do not belong to the user.

Step-by-step guide: Patch Management Checklist: Secure Systems Without Breaking Them

General security guidance from the Firewall Scoop newsroom. It is not confirmed advice from the organisations named in this story.

Frequently asked questions

What is the CVSS score for CVE-2026-77366?

The CVSS score is 9.9, which is rated as critical.

Which software vendor is affected by this flaw?

The vendor is The-40-Thieves, and the product is obsidian-tc.

Does version 1.3.1 fix the vulnerability?

Yes, version 1.3.1 fixes the vulnerability by binding tokens to vaults.