AS-2026-021: ABP and AES

2026-08-04

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Statement

An improper authentication and path traversal vulnerability exists in ASUSTOR Backup Plan (ABP) and ASUSTOR EZ Sync (AES). A local attacker can submit crafted encrypted requests containing directory traversal sequences to perform arbitrary file reads and arbitrary file writes as NT AUTHORITY\SYSTEM, leading to full local privilege escalation.
Affected products and versions include: ABP (ASUSTOR Backup Plan) 2.0.7.10171 and earlier as well as AES (ASUSTOR EZSync) 1.1.1.3113 and earlier.

Affected Products

Product	Severity	Fixed Release Availability
ABP (ASUSTOR Backup Plan)	Important	Ongoing
AES (ASUSTOR EZSync)	Important	Ongoing

Detail

• CVE-2026-18759
  • Severity: High
  • CVSS4 Base Score: 8.5
  • CVSS4 Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
  • The background service of ABP or AES runs as NT AUTHORITY\SYSTEM and implements a file-based inter-process communication (IPC) mechanism protected by AES encryption. Because the encryption key file is readable by standard users and protected using DPAPI. Any authenticated local user can recover the key and forge valid IPC requests. Furthermore, the service does not check the identity of the requesting process and validates destination paths using an insufficient substring check. A local attacker can submit crafted encrypted requests containing directory traversal sequences to perform arbitrary file reads and arbitrary file writes as NT AUTHORITY\SYSTEM, leading to full local privilege escalation. Affected products and versions include: ABP (ASUSTOR Backup Plan) 2.0.7.10171 and earlier as well as AES (ASUSTOR EZSync) 1.1.1.3113 and earlier.

Reference

• CVE-2026-18759

Acknowledgement

Kazuma Matsumoto, Security Researcher at GMO Cybersecurity by IERAE, Inc.

Revision

Revision	Date	Description
1	2026-08-03	Initial public release.
2	2026-08-04	CVE ID (CVE-2026-18759) is assigned for the issue.