How severe is CVE-2026-77366?

CVE-2026-77366 has a CVSS score of 9.9/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-77366?

CVE-2026-77366 affects the following packages: obsidian-tc (npm). Ecosystems affected: npm.

How do I fix CVE-2026-77366?

Update obsidian-tc to 1.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-77366 is resolved across your whole dependency graph.

How do I detect CVE-2026-77366 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for obsidian-tc, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-77366 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2026-77366 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-77366 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

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

CVE-2026-77366 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 22th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-77366?

CVE-2026-77366 is classified as CWE-639 (CWE-639), CWE-863 (CWE-863). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-77366 published, and has it been updated?

CVE-2026-77366 was published on October 12, 2026 and was last updated on October 24, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

CRITICAL severity

CVE-2026-77366 — obsidian-tc

CRITICALFix: The-40-Thieves/obsidian-tc@38b4992

CVE-2026-77366 is a critical-severity (CVSS 9.9) CWE-639 vulnerability in obsidian-tc. A fix is available for obsidian-tc — see the affected versions and patch details below.

obsidian-tc tokens can access arbitrary configured vaults

Also known asGHSA-84c9-qqpq-2pq5

Published

Oct 12, 2026

Updated

Oct 24, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-77366.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs22th percentile — riskier than 22% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-77366 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

0other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

obsidian-tcnpm

938downloads / week

Description

Impact

Tool dispatch did not check the caller-supplied input.vault against the caller's bound vault (ctx.vaultId); the folder ACL was a single global instance and the JWT carried no vault claim. As a result, any valid token could read, write, or delete any configured vault by passing input.vault, defeating multi-tenant isolation across ~90 tool sites. (resources/read was the only surface that already guarded this.)

Patches

Fixed in 1.3.1 (the fix was developed on the v1.3.0 tag, which never published to npm; 1.3.1 is the first published release with the fix). Upgrade to >= 1.3.1.

Workarounds

Run a single vault per server process, or isolate each tenant on a separate process/credential.

Fix

A central input.vault === ctx.vaultId guard was added in dispatch before the scope check.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`obsidian-tc`	all versions	1.3.1`npm install obsidian-tc@1.3.1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for obsidian-tc, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update obsidian-tc to 1.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-77366 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

### Impact Tool dispatch did not check the caller-supplied `input.vault` against the caller's bound vault (`ctx.vaultId`); the folder ACL was a single global instance and the JWT carried no vault claim. As a result, **any valid token could read, write, or delete any configured vault** by passing `input.vault`, defeating multi-tenant isolation across ~90 tool sites. (`resources/read` was the only surface that already guarded this.) ### Patches Fixed in **1.3.1** (the fix was developed on the `v1.3.0` tag, which never published to npm; 1.3.1 is the first published release with the fix). Upgrade