SB20260423158 - Missing Authentication for Critical Function in nginx-ui

Description

This security bulletin contains information about 1 vulnerability.

1) Missing Authentication for Critical Function (CVE-ID: CVE-2026-27944)

CWE-ID: CWE-306 - Missing Authentication for Critical Function

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/U:Amber

The vulnerability allows a remote attacker to download and decrypt a full system backup containing sensitive information.

The vulnerability exists due to missing authentication for critical function in the /api/backup endpoint when handling unauthenticated backup requests. A remote attacker can send a crafted GET request to download and decrypt a full system backup containing sensitive information.

The AES-256 key and IV are disclosed in the X-Backup-Security response header, and the backup may contain user credentials, session tokens, SSL private keys, and nginx configuration data.

Remediation

Install update from vendor's website.

References

• https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-g9w5-qffc-6762
• https://github.com/advisories/GHSA-g9w5-qffc-6762