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Nginx UI - Unauthenticated Backup Download with Encryption Key Disclosure

Critical

Synopsis

The /api/backup endpoint is accessible without authentication and discloses the encryption keys required to decrypt the backup in the X-Backup-Security response header. This allows an unauthenticated attacker to download a full system backup containing sensitive data (user credentials, session tokens, SSL private keys, Nginx configurations) and decrypt it immediately.

Solution

Upgrade to Nginx UI version 2.3.3 or later.

Disclosure Timeline

Jan 29, 2026 : Initial contact - Report submitted via GitHub
Jan 29, 2026 : Vendor Acknowledgement
Jan 29, 2026 : Vulnerability fixed on `dev`
Feb 04, 2026 : Vendor indicates that a release will be made as soon as possible.
Feb 15, 2026 : Vendor has released version 2.3.3 with the fix.

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