CVE-2026-66005

Jan Local API Server CORS Origin Reflection via 0.0.0.0 Binding

State: Published
Severity: 5.3 Medium
Published: Jul 24, 2026
Updated: Sep 17, 2026
Reserved: Jul 23, 2026

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.

Scores

CVSS	Score	Vector	Source
4.0	5.3 Medium	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N	VulnCheck
3.1	6.3 Medium	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L	VulnCheck

Weaknesses

CWE-183 Permissive List of Allowed Inputs
CWE-942 Permissive Cross-domain Security Policy with Untrusted Domains

Affected Products

Product	Versions
janjanhq	0.8.4 and earlierAffected 3e1c1e724f696620d89bb4a9cc18a380e0753757Not affected

References

Researcher Disclosuretechnical-descriptionexploitissue-tracking
Pull Requestissue-trackingpatch
Patch Commitpatch
https://www.vulncheck.com/advisories/jan-local-api-server-cors-origin-reflection-via-bindingthird-party-advisory

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