CVE-2026-77366 in obsidian-tc
Summary
by MITRE • 10/12/2026
obsidian-tc is a governed, agent-ready Model Context Protocol server for Obsidian vaults. Prior to 1.3.1, tool dispatch does not compare the caller-controlled input.vault value with the vault bound to the caller, the JSON Web Token (JWT) has no vault claim, and the folder access-control list is shared globally. Any valid token can therefore select another configured vault and read, write, or delete its contents through affected tools. Version 1.3.1 fixes the vulnerability by binding tokens and request context to a vault and rejecting mismatched input.vault values before scope checks.
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Analysis
by VulDB Data Team • 10/13/2026
The obsidian-tc server, which serves as an agent-ready Model Context Protocol interface for Obsidian knowledge bases, suffered from a critical access control flaw in versions prior to 1.3.1 that allowed unauthorized cross-vault data manipulation. This vulnerability stems from the absence of strict identity verification and scope enforcement mechanisms within the tool dispatch logic. Specifically, the application failed to validate whether the vault identifier provided by the caller matched the specific vault associated with their authenticated session or token. Furthermore, the JSON Web Tokens issued for authentication lacked a dedicated claim specifying the authorized vault context, rendering them generic rather than scoped to individual data stores.
The operational impact of this flaw is severe, as it effectively neutralizes multi-tenant isolation within the system. Because folder access control lists were shared globally across all configured vaults and tokens did not carry specific vault permissions, any user possessing a valid authentication token could arbitrarily select another user's or tenant's vault identifier in their API requests. This lack of separation allowed attackers to read sensitive notes, write malicious content, or delete critical data belonging to other users without needing additional credentials for those target vaults. The vulnerability represents a classic failure in object level access control where the server trusts client-supplied identifiers over server-side session state.
From a classification perspective, this issue aligns with CWE-284 Improper Access Control and CWE-613 Insufficient Session Expiration or Termination if tokens were not properly scoped to prevent reuse across contexts. In terms of adversary tactics, it facilitates lateral movement within the application layer by allowing an attacker to pivot from one compromised vault context to another using a single set of credentials, similar to techniques observed in ATT&CK ID T1078 Valid Accounts where existing valid accounts are used to access resources they should not have permission to view or modify.
The vulnerability was resolved in version 1.3.1 by implementing strict binding between authentication tokens and specific vault contexts. The updated logic ensures that the input.vault value is compared against the vault bound to the caller's session before any scope checks are performed. If a mismatch occurs, the request is rejected immediately, thereby enforcing proper isolation boundaries. To mitigate similar risks in other systems, developers should ensure that JWTs contain explicit claims defining resource scopes and implement server-side validation of all client-supplied identifiers against established session contexts rather than relying on implicit trust or global access lists.