Vulnerability · Published Jul 24, 2026 · Assigned by VulnCheck

CVE-2026-66005Jan Local API Server CORS Origin Reflection via 0.0.0.0 Binding

Medium 6.3

In plain English

A medium-severity security flaw in jan from janhq. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 26% of all known vulnerabilities).

Severity (CVSS 3.1)6.3Medium

Exploit odds (30 days)0.3%top 73.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
janhq	jan	0 – through 0.8.4

Weakness: CWE-183, CWE-942 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L

References

Researcher Disclosure technical-description, exploit, issue-tracking
Pull Request issue-tracking, patch
Patch Commit patch
https://www.vulncheck.com/advisories/jan-local-api-server-cors-origin-reflection-via-binding third-party-advisory