CVE-2026-77363 The-40-Thieves CVE debrief

Who should care

Defenders of Obsidian vaults using obsidian-tc should assess exposure and prioritize upgrading to version 1.3.1 or later to prevent potential unrestricted vault access. This includes reviewing and adjusting loopback configurations, monitoring for suspicious activity, and verifying obsidian-tc versions and configurations.

Why it matters

Defenders of Obsidian vaults using obsidian-tc should assess exposure and prioritize upgrading to version 1.3.1 or later to prevent potential unrestricted vault access.

• Potential unrestricted vault access through http-local caller
• Requires verification of obsidian-tc versions and configurations

Technical summary

obsidian-tc Streamable HTTP transport permits cross-origin loopback vault access due to lack of Host or Origin header validation and DNS-rebinding protection. This allows a malicious web page to send requests to the local MCP endpoint and receive unrestricted vault access through the http-local caller when the loopback configuration uses auth.mode set to none. The vulnerability is fixed in version 1.3.1, which enables host, origin, and DNS-rebinding validation. Defenders should prioritize verifying obsidian-tc versions and upgrading to 1.3.1 or later.

Defensive priority

Defenders should prioritize verifying obsidian-tc versions and upgrading to 1.3.1 or later.

Recommended defensive actions

• Verify obsidian-tc version and upgrade to 1.3.1 or later
• Review and adjust loopback configuration
• Monitor for suspicious activity
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and source item provide details on the vulnerability in obsidian-tc Streamable HTTP transport. The vulnerability allows for cross-origin loopback vault access due to a lack of Host or Origin header validation and DNS-rebinding protection. Defenders should verify obsidian-tc versions and configurations to assess exposure. The CVE record was published on 2026-10-12T17:45:57.107Z and has not been modified since then.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.