Improper input validation in Chatgptnextweb Nextchat
CVE-2026-82639
NextChat versions from 2.15.8 through 2.16.1 contain an improper URL validation vulnerability in the proxy endpoint that allows attackers to obtain the server's OpenAI API key. The x-base-url header is validated using substring matching instead of hostname parsing, allowing any URL containing 'api.openai.com' to pass validation and receive the server's credentials in the Authorization header.
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.005 (42.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 42nd percentile — 42.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002
Affected products
Weakness classification (CWE)
References
- GitHub Issue #6814 (issue-tracking)
- github.com/ChatGPTNextWeb/NextChat (product)
- github.com/ChatGPTNextWeb/NextChat/blob/v2.16.1/app/api/proxy.ts (technical-description)
- VulnCheck Advisory: NextChat 2.15.8 through 2.16.1 OpenAI API Key Disclosure (third-party-advisory)
Frequently asked questions
- What is CVE-2026-82639?
- CVE-2026-82639 is a high-severity vulnerability in Chatgptnextweb Nextchat, classified under Improper Input Validation. CVSS score: 7.5/10. Published 2026-08-30.
- How severe is CVE-2026-82639?
- High severity. CVSS v3 base score is 7.5 out of 10.