CVE-2026-77363: obsidian-tc HTTP transport lacks Origin/DNS-rebinding protection, enabling drive-by vault access on loopback

Should you act?

Normal patch cycle

No exploitation signal; fix it in your next routine update if you are affected. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.2%, percentile 5: FIRST’s model estimates a 0.2% chance of exploitation activity in the next 30 days, higher than 5% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Needs a user to click or open something. Phishing makes that realistic, but it is not wormable.
• Only applies if your dependency tree includes obsidian-tc (npm) < 1.3.1, fixed in 1.3.1. Check your lockfile, including transitive dependencies.

What it is

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.

From the GitHub advisory

Impact The Streamable HTTP transport was constructed without enableDnsRebindingProtection/allowedHosts/allowedOrigins and performed no Origin-header validation. With the documented auth.mode: "none" loopback default, a drive-by web page could POST http://127.0.0.1/mcp and receive caller http-local with scopes [""] — full vault read/write — via DNS rebinding / a forged Origin.

Patches Fixed in 1.3.1. Upgrade to >= 1.3.1. The transport now enables DNS-rebinding protection and allowed hosts/origins and returns HTTP 403 on an invalid Origin (per MCP 2025-11-25).

Workarounds Do not expose the HTTP transport with auth.mode: "none"; require JWT auth, or bind to a non-loopback interface behind a proxy that validates Origin.

Weakness type: CWE-346, CWE-1385.

Product: obsidian-tc (npm) · Assigned by: GitHub_M · Published: 2026-10-12

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: required (a user must click/open something)
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-23): 0.16% probability of exploitation activity in the next 30 days; percentile 5.

Timeline

• 2026-10-12 — CVE record published by GitHub_M
• 2026-10-13 — CVE record last updated
• 2026-10-23 — GitHub-reviewed advisory GHSA-pqh8-4pj7-32xx published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-pqh8-4pj7-32xx github.com
2. CVE.org record CVE-2026-77363 cve.org
3. NVD entry CVE-2026-77363 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com
5. nvd.nist.gov nvd.nist.gov

Critical npm advisories · Today’s Security Digest