CVE-2026-28727: Acronis Cyber Protect Escalation Flaw

CVE-2026-28727 Overview

CVE-2026-28727 is a local privilege escalation vulnerability affecting Acronis Cyber Protect products on macOS. The vulnerability stems from insecure Unix socket permissions, which allows a local attacker with low privileges to escalate their access and gain elevated permissions on the affected system. This weakness (CWE-276: Incorrect Default Permissions) occurs when Unix sockets are created with overly permissive access controls, enabling unauthorized users to interact with privileged services.

Critical Impact

Local attackers can exploit insecure Unix socket permissions to achieve privilege escalation, potentially gaining full control over the affected macOS system running Acronis Cyber Protect software.

Affected Products

• Acronis Cyber Protect 17 (macOS) before build 41186
• Acronis Cyber Protect Cloud Agent (macOS) before build 41124

Discovery Timeline

• 2026-03-06 - CVE CVE-2026-28727 published to NVD
• 2026-03-09 - Last updated in NVD database

Technical Details for CVE-2026-28727

Vulnerability Analysis

This vulnerability represents a classic case of Incorrect Default Permissions (CWE-276) affecting the inter-process communication mechanism used by Acronis Cyber Protect products on macOS. Unix sockets are commonly used for local communication between processes, and when configured with improper permissions, they can become a vector for privilege escalation attacks.

The affected Acronis software creates Unix domain sockets that inadvertently allow access from unprivileged local users. Since these sockets facilitate communication with components running at elevated privilege levels, an attacker who can connect to and interact with these sockets may be able to issue commands or manipulate the privileged service to perform unauthorized actions.

Root Cause

The root cause of CVE-2026-28727 lies in the improper configuration of file system permissions for Unix domain sockets created by the Acronis Cyber Protect agent on macOS. When the application initializes its communication sockets, it fails to restrict access appropriately, resulting in world-readable or world-writable socket files. This allows any local user to establish connections to the socket and potentially interact with the privileged daemon.

Attack Vector

The attack vector for this vulnerability is local, requiring the attacker to have an existing account on the target macOS system. The attack follows this general pattern:

1. The attacker identifies the location of the insecure Unix socket created by the Acronis Cyber Protect agent
2. The attacker crafts malicious requests or commands to send through the socket
3. By exploiting the permissive socket permissions, the attacker connects to the privileged service
4. The privileged service processes the attacker's requests, leading to unauthorized actions being performed with elevated privileges

The vulnerability requires low privileges to exploit and does not require user interaction, making it particularly dangerous in multi-user environments or systems where attackers have gained initial foothold with limited access.

Detection Methods for CVE-2026-28727

Indicators of Compromise

• Unexpected connections to Acronis-related Unix sockets from non-privileged user processes
• Suspicious process behavior associated with the Acronis Cyber Protect agent, such as spawning unusual child processes
• File permission changes on Acronis-related socket files or configuration directories

Detection Strategies

• Monitor for unusual socket connections using tools like lsof or netstat to identify processes connecting to Acronis Unix sockets
• Implement file integrity monitoring on Acronis installation directories to detect unauthorized modifications
• Review system logs for privilege escalation attempts or unexpected authentication events associated with Acronis services
• Use endpoint detection tools to identify anomalous process relationships and privilege changes

Monitoring Recommendations

• Configure logging for socket access events on macOS systems running affected Acronis products
• Establish baseline behavior for Acronis Cyber Protect processes and alert on deviations
• Monitor for new local user account creation or privilege changes that could indicate post-exploitation activity

How to Mitigate CVE-2026-28727

Immediate Actions Required

• Update Acronis Cyber Protect 17 (macOS) to build 41186 or later immediately
• Update Acronis Cyber Protect Cloud Agent (macOS) to build 41124 or later immediately
• Audit current Unix socket permissions on affected systems to identify potential exposure
• Review local user accounts and remove unnecessary access to systems running affected software

Patch Information

Acronis has released updated builds that address this vulnerability. For Acronis Cyber Protect 17 on macOS, users should upgrade to build 41186 or later. For Acronis Cyber Protect Cloud Agent on macOS, users should upgrade to build 41124 or later. Detailed patch information is available in the Acronis Security Advisory SEC-9408.

Workarounds

• Restrict local user access to systems running affected Acronis products until patches can be applied
• Implement additional access controls using macOS system policies to limit socket access
• Consider temporarily disabling affected services in high-risk environments where immediate patching is not possible
• Monitor affected systems closely for signs of exploitation while awaiting patch deployment

# Check current Unix socket permissions for Acronis-related sockets
ls -la /var/run/acronis* /tmp/acronis* 2>/dev/null

# Verify Acronis Cyber Protect version
/Library/Application\ Support/Acronis/Agent/aakore --version