CVE-2026-3991: Symantec DLP Privilege Escalation Flaw

CVE-2026-3991 Overview

CVE-2026-3991 is an Elevation of Privilege vulnerability affecting Symantec Data Loss Prevention (DLP) Windows Endpoint software. This security flaw allows an attacker with local access and limited privileges to potentially gain elevated access to resources that are normally protected from standard applications or users. The vulnerability is classified under CWE-829 (Inclusion of Functionality from Untrusted Control Sphere), indicating the software may improperly include functionality from an untrusted source.

Critical Impact

Local attackers with low privileges can potentially escalate their permissions to gain high-level access, compromising system confidentiality, integrity, and availability on enterprise endpoints protected by Symantec DLP.

Affected Products

• Symantec Data Loss Prevention Windows Endpoint prior to 25.1 MP1
• Symantec Data Loss Prevention Windows Endpoint prior to 16.1 MP2
• Symantec Data Loss Prevention Windows Endpoint prior to 16.0 RU2 HF9
• Symantec Data Loss Prevention Windows Endpoint prior to 16.0 RU1 MP1 HF12
• Symantec Data Loss Prevention Windows Endpoint prior to 16.0 MP2 HF15

Discovery Timeline

• 2026-03-30 - CVE-2026-3991 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2026-3991

Vulnerability Analysis

This vulnerability affects Symantec Data Loss Prevention Windows Endpoint agents, which are security software components designed to protect sensitive enterprise data on Windows workstations. The flaw enables privilege escalation through a weakness categorized as CWE-829: Inclusion of Functionality from Untrusted Control Sphere.

CWE-829 vulnerabilities occur when software incorporates executable functionality from a source outside of its intended trust boundary. In the context of a DLP endpoint agent, this could involve the software loading or executing code, libraries, or modules from locations that an attacker can control or influence.

The local attack vector requires an attacker to already have some level of access to the target system. However, the low privilege requirement means that even a standard user account could potentially exploit this vulnerability. Once exploited, the attacker gains elevated permissions with high impact to confidentiality, integrity, and availability—effectively achieving complete control over the affected endpoint.

Root Cause

The root cause stems from the inclusion of functionality from an untrusted control sphere (CWE-829). This typically manifests when privileged endpoint security software loads executable code, plugins, or libraries from paths that low-privileged users can write to or manipulate. The DLP agent, running with elevated system privileges, may inadvertently execute attacker-controlled code, resulting in privilege escalation.

Attack Vector

The attack requires local access to the system with low-privilege credentials. An attacker could exploit this vulnerability by:

1. Gaining initial access to the target Windows endpoint with a standard user account
2. Identifying writable locations that the privileged DLP agent process references for loading functionality
3. Placing malicious code or libraries in these controllable paths
4. Triggering the DLP agent to load the attacker-controlled functionality
5. Executing arbitrary code within the context of the privileged DLP agent process

The vulnerability can be exploited without any user interaction once the attacker has local access. The technical implementation details involve the DLP endpoint agent's trust model for loading external functionality. For complete technical details, refer to the Broadcom Security Advisory #37306.

Detection Methods for CVE-2026-3991

Indicators of Compromise

• Unexpected DLL or executable files appearing in directories accessible to the Symantec DLP agent
• Process creation events showing the DLP agent spawning unusual child processes
• File system changes in DLP installation or plugin directories by non-administrative users
• Anomalous registry modifications related to Symantec DLP component paths

Detection Strategies

• Monitor for file creation events in Symantec DLP installation directories and any paths referenced by the agent
• Implement process monitoring to detect the DLP agent loading modules from non-standard or user-writable locations
• Deploy endpoint detection rules to alert on privilege escalation attempts involving edpa.exe or related DLP processes
• Use SentinelOne's behavioral AI to detect anomalous privilege escalation patterns from DLP agent processes

Monitoring Recommendations

• Enable detailed Windows Security Event logging for process creation (Event ID 4688) with command-line auditing
• Configure Sysmon to capture module load events (Event ID 7) for DLP-related processes
• Implement file integrity monitoring on critical Symantec DLP directories
• Review SentinelOne console alerts for behavioral indicators associated with local privilege escalation

How to Mitigate CVE-2026-3991

Immediate Actions Required

• Inventory all Symantec DLP Windows Endpoint installations and identify systems running vulnerable versions
• Prioritize patching based on system criticality and exposure to untrusted local users
• Apply the principle of least privilege to limit user accounts that have local access to systems with DLP agents
• Review and restrict write permissions on directories related to the DLP agent installation

Patch Information

Broadcom has released patched versions addressing this vulnerability. Organizations should upgrade to one of the following fixed versions:

• Symantec DLP Windows Endpoint 25.1 MP1 or later
• Symantec DLP Windows Endpoint 16.1 MP2 or later
• Symantec DLP Windows Endpoint 16.0 RU2 HF9 or later
• Symantec DLP Windows Endpoint 16.0 RU1 MP1 HF12 or later
• Symantec DLP Windows Endpoint 16.0 MP2 HF15 or later

For detailed patch information and download links, consult the Broadcom Security Advisory #37306.

Workarounds

• Restrict local logon rights on systems with DLP agents to only essential personnel
• Implement application whitelisting to prevent unauthorized executables from running in DLP-related directories
• Use Windows security features such as AppLocker or Windows Defender Application Control to restrict code execution
• Deploy SentinelOne's protection capabilities to detect and block privilege escalation attempts in real-time

# Example: Restrict write permissions on Symantec DLP directories
icacls "C:\Program Files\Symantec\Data Loss Prevention" /inheritance:r /grant:r "SYSTEM:(OI)(CI)F" /grant:r "Administrators:(OI)(CI)F" /grant:r "BUILTIN\Users:(OI)(CI)RX"