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Vulnerability record · CVE-2026-82639 · published 30 August 2026

CVE-2026-82639: Improper input validation vulnerability

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.

8.7 CVSS 4.0 High EPSS 0.51% · top 59.0% CWE-20 · Improper input validation Deferred
8.7CVSS 4.0 base score
0.51%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
5References
10 Sep 2026Last modified by NVD

Description

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/ChatGPTNextWeb/NextChat
https://github.com/ChatGPTNextWeb/NextChat/blob/v2.16.1/app/api/proxy.ts
https://github.com/ChatGPTNextWeb/NextChat/issues/6814
https://www.vulncheck.com/advisories/nextchat-2.15.8-through-2.16.1-openai-api-key-disclosure
https://github.com/ChatGPTNextWeb/NextChat/issues/6814

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Source: NIST National Vulnerability Database (record CVE-2026-82639), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.