CVE-2026-82639: Improper Input Validation in ChatGPTNextWeb NextChat
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 v4.0
Score 8.7high
Affected software
ChatGPTNextWeb
NextChat
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-82639 affects NextChat versions from 2.15.8 to 2.16.1. The vulnerability is due to improper input validation of the x-base-url header in the proxy endpoint. Instead of correctly parsing the hostname, the validation uses substring matching, which can be bypassed by URLs containing 'api.openai.com' as a substring. This allows an attacker to retrieve the server's OpenAI API key included in the Authorization header, potentially compromising the server's credentials.
Potential Impact
An attacker can obtain the server's OpenAI API key by exploiting the improper URL validation. This exposure could lead to unauthorized use of the API key, potentially incurring costs or misuse of the OpenAI service under the server's account. The CVSS score of 8.7 indicates a high severity vulnerability with network attack vector, no privileges or user interaction required, and high impact on confidentiality.
Mitigation Recommendations
No explicit patch or remediation information is provided in the input data. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, avoid using affected versions or restrict access to the proxy endpoint to trusted users only.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-08-30T13:06:02.366Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a943230acd9273b4997c70c
Added to database: 08/30/2026, 13:37:52 UTC
Last enriched: 09/25/2026, 02:45:37 UTC
Last updated: 10/14/2026, 06:48:21 UTC
Views: 93
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