CVE-2026-66005 Details
Description
Jan through 0.8.4, fixed in commit 3e1c1e7, contains a CORS misconfiguration vulnerability in its local API server that allows network-adjacent attackers to bypass trusted host restrictions by exploiting the server's replacement of user-configured trusted hosts with a wildcard that reflects arbitrary origins with credentials. Attackers on the local network or using DNS rebinding can reach the unauthenticated OpenAI-compatible API to perform inference, enumerate models, invoke MCP tools, and read cross-origin responses.
A CORS misconfiguration vulnerability has been identified in Jan versions through 0.8.4. This vulnerability resides in the local API server, where user-configured trusted hosts are replaced with a wildcard, allowing arbitrary origins to be reflected with credentials. As a result, network-adjacent attackers can bypass trusted host restrictions and access the unauthenticated OpenAI-compatible API. Exploitation can lead to unauthorized model inference, model enumeration, invocation of MCP tools, and cross-origin reading of API responses. The issue is compounded by the fact that the UI 'CORS enabled' toggle is non-functional.
Users should avoid binding the local API server to '0.0.0.0' without a properly configured Trusted Hosts allowlist. If the server must be exposed on the network, ensure that the allowlist is set to accept only trusted hosts. Additionally, the CORS Origin allowlist should be managed independently of the Host header validation.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Jul 24, 2026CISA-ADP
Assessed Jul 24, 2026References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.
| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/janhq/jan/commit/3e1c1e724f696620d89bb4a9cc18a380e0753757 | [email protected] | Source CodeVendor |
| https://github.com/janhq/jan/issues/8453 | [email protected] | ExploitIssue TrackingTechnical DescriptionVendor |
| https://github.com/janhq/jan/pull/8506 | [email protected] | Issue TrackingVendor |
| https://www.vulncheck.com/advisories/jan-local-api-server-cors-origin-reflection-via-binding | [email protected] | AdvisoryBundleRemedy |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-183 | Permissive List of Allowed Inputs | [email protected] |
| CWE-942 | Permissive Cross-domain Policy with Untrusted Domains | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| Jan | <= 0.8.4 (semver) |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 17, 2026 | CVE Modified | [email protected] |
| Jul 24, 2026 | CVE Modified | CISA-ADP |
| Jul 24, 2026 | New CVE Received | [email protected] |