API key disclosure via substring URL validation
Published Aug 30, 2026 · Updated Aug 30, 2026
Improper URL validation in NextChat 2.15.8 through 2.16.1 allows remote attackers to steal the server's OpenAI API key. The app/api/proxy.ts handler tests the attacker-controlled x-base-url header with substring matching and adds the key to an outbound Authorization header. The proxy route requires no authentication; exploitation requires a server configured with OPENAI_API_KEY and discloses that credential to an attacker-controlled host.
Summary
What happened
Improper URL validation in NextChat 2.15.8 through 2.16.1 allows remote attackers to steal the server's OpenAI API key. The app/api/proxy.ts handler tests the attacker-controlled x-base-url header with substring matching and adds the key to an outbound Authorization header. The proxy route requires no authentication; exploitation requires a server configured with OPENAI_API_KEY and discloses that credential to an attacker-controlled host.
The record
- CVE
- CVE-2026-82639
- Published
- Aug 30, 2026
- Updated
- Aug 30, 2026
- Vendor
- ChatGPTNextWeb
- Product
- NextChat
- Classifications
- T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 30, 2026CVE publishedPublication date reported by the CVE source.
- Aug 30, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=2.15.8 <=2.16.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Unauthenticated x-base-url API-key exfiltration proof of conceptfunctional · demonstrated
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Technologies
Your stack
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Your stack
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