CVE-2026-28720: Acronis Cyber Protect Auth Bypass Flaw

CVE-2026-28720 Overview

CVE-2026-28720 is an authorization bypass vulnerability affecting Acronis Cyber Protect 17. The vulnerability stems from insufficient authorization checks that allow authenticated users to perform unauthorized modification of settings. This flaw enables attackers with low-level privileges to alter system configurations they should not have access to modify.

Critical Impact

Authenticated attackers can modify system settings without proper authorization, potentially compromising the integrity of backup and protection configurations in enterprise environments.

Affected Products

• Acronis Cyber Protect 17 (Linux) before build 41186
• Acronis Cyber Protect 17 (Windows) before build 41186

Discovery Timeline

• 2026-03-06 - CVE CVE-2026-28720 published to NVD
• 2026-03-09 - Last updated in NVD database

Technical Details for CVE-2026-28720

Vulnerability Analysis

This vulnerability is classified under CWE-863 (Incorrect Authorization), indicating that the application fails to properly verify that a user has the necessary permissions before allowing them to perform privileged actions. In the context of Acronis Cyber Protect 17, this manifests as a failure to validate authorization when users attempt to modify system settings.

The attack can be executed remotely over the network by any authenticated user with low-level privileges. No user interaction is required for exploitation. While the vulnerability does not directly impact confidentiality or availability, it allows unauthorized integrity violations through settings modification.

Root Cause

The root cause lies in insufficient authorization checks within the settings modification functionality of Acronis Cyber Protect 17. The application fails to properly validate whether the authenticated user has the appropriate role or permissions to modify specific settings, allowing users with limited privileges to alter configurations reserved for administrators or higher-privileged accounts.

Attack Vector

The attack vector is network-based with low complexity requirements. An attacker must first authenticate to the system with valid credentials, even if those credentials provide only minimal access. Once authenticated, the attacker can directly access and modify settings that should be protected by role-based access controls. The lack of proper authorization validation means the application relies solely on authentication without enforcing granular permission checks.

The vulnerability does not require any special conditions or user interaction beyond the initial authentication, making it relatively straightforward to exploit once network access to the Acronis Cyber Protect management interface is obtained.

Detection Methods for CVE-2026-28720

Indicators of Compromise

• Unexpected changes to Acronis Cyber Protect configuration settings without corresponding administrative activity logs
• Settings modifications performed by user accounts that should not have administrative privileges
• Audit log entries showing configuration changes from unusual IP addresses or user sessions

Detection Strategies

• Monitor Acronis Cyber Protect audit logs for settings modification events performed by non-administrative users
• Implement alerting for configuration changes outside of scheduled maintenance windows
• Review user activity logs to identify accounts accessing settings endpoints they should not have permission to modify

Monitoring Recommendations

• Enable verbose logging for all settings modification operations within Acronis Cyber Protect
• Configure SIEM integration to correlate user permissions with administrative actions
• Establish baseline configuration snapshots and alert on unauthorized deviations

How to Mitigate CVE-2026-28720

Immediate Actions Required

• Update Acronis Cyber Protect 17 to build 41186 or later immediately
• Review recent settings changes for any unauthorized modifications made prior to patching
• Audit user accounts and remove unnecessary access privileges following the principle of least privilege
• Monitor for suspicious configuration changes until patching is complete

Patch Information

Acronis has addressed this vulnerability in Acronis Cyber Protect 17 build 41186. Organizations should update to this version or later to remediate the authorization bypass. Detailed patch information is available in the Acronis Security Advisory SEC-8379.

Workarounds

• Restrict network access to the Acronis Cyber Protect management interface to trusted IP addresses only
• Implement additional network segmentation to limit which users can reach the management console
• Review and minimize the number of user accounts with any level of access to the system until patching can be completed

# Example: Restrict management interface access via firewall (Linux)
# Allow only trusted admin networks to access Acronis management port
iptables -A INPUT -p tcp --dport 9877 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 9877 -j DROP