CVE-2021-47831: Sandboxie 5.49.7 DoS Vulnerability

CVE-2021-47831 Overview

CVE-2021-47831 is a denial of service vulnerability affecting Sandboxie version 5.49.7. The vulnerability allows attackers to crash the application by overflowing the container folder input field. By pasting a large buffer of repeated characters into the Sandbox container folder setting, an attacker can trigger an application crash, disrupting the sandboxing functionality and potentially leaving systems unprotected.

Critical Impact

Attackers can cause Sandboxie to crash by exploiting improper input validation in the container folder configuration field, potentially leaving sandboxed applications unprotected.

Affected Products

• Sandboxie 5.49.7
• Sandboxie Plus (potentially affected versions)

Discovery Timeline

• 2026-01-16 - CVE-2021-47831 published to NVD
• 2026-01-16 - Last updated in NVD database

Technical Details for CVE-2021-47831

Vulnerability Analysis

This vulnerability is classified under CWE-1284 (Improper Validation of Specified Quantity in Input). The core issue lies in the application's failure to properly validate the length or size of user-supplied input in the Sandbox container folder configuration field. When a user or attacker pastes an excessively long string of characters into this field, the application fails to handle the oversized input gracefully, resulting in an application crash.

The local attack vector requires user interaction, as the attacker must either have local access to the system or convince a user to paste malicious input into the configuration field. While the impact is limited to availability (denial of service) without direct compromise of confidentiality or integrity, the disruption of Sandboxie's protective capabilities could expose sandboxed applications to threats during the crash period.

Root Cause

The root cause of this vulnerability is improper input validation in the Sandbox container folder setting. The application does not implement adequate boundary checks or input length restrictions on the folder path field. When an extremely long string is provided, the application's internal buffer handling mechanisms fail to accommodate the oversized input, leading to memory corruption or an unhandled exception that causes the crash.

Attack Vector

The attack requires local access to the Sandboxie application and user interaction to execute. An attacker would need to:

1. Access the Sandboxie configuration interface
2. Navigate to the Sandbox container folder setting
3. Paste a large buffer of repeated characters into the input field
4. Trigger the configuration change, causing the application to crash

The attack is reproducible and documented in public exploit databases. Technical details are available in the Exploit-DB #49844 entry.

Detection Methods for CVE-2021-47831

Indicators of Compromise

• Unexpected Sandboxie application crashes or terminations
• Event log entries indicating application faults in SbieCtrl.exe or related Sandboxie processes
• Unusually long folder path strings in Sandboxie configuration files
• User reports of Sandboxie instability after configuration changes

Detection Strategies

• Monitor Windows Event Logs for application crash events related to Sandboxie components (SbieCtrl.exe, SbieSvc.exe)
• Implement endpoint detection rules for abnormal process terminations of Sandboxie services
• Use file integrity monitoring to detect unauthorized or suspicious changes to Sandboxie configuration files
• Deploy SentinelOne Singularity to detect anomalous application behavior patterns indicative of exploitation attempts

Monitoring Recommendations

• Configure alerting for repeated Sandboxie process crashes within short time windows
• Monitor clipboard activity for unusually large text buffers being pasted into Sandboxie configuration interfaces
• Establish baseline behavior for Sandboxie processes to identify deviations
• Review Sandboxie configuration files periodically for abnormally long path entries

How to Mitigate CVE-2021-47831

Immediate Actions Required

• Upgrade to a patched version of Sandboxie Plus from the official website
• Restrict local access to systems running vulnerable Sandboxie versions
• Implement application allowlisting to prevent unauthorized configuration changes
• Consider alternative sandboxing solutions until the upgrade is complete

Patch Information

Users should upgrade to the latest version of Sandboxie Plus, which addresses this input validation vulnerability. The Sandboxie project is now maintained as Sandboxie Plus, an open-source continuation of the original software. Visit the Sandboxie Plus Homepage for the latest secure release.

Additional advisory information is available from VulnCheck Sandboxie Advisory.

Workarounds

• Limit user access to Sandboxie configuration settings through Windows permissions or Group Policy
• Avoid pasting untrusted content into Sandboxie configuration fields
• Implement user training to recognize and avoid potential exploitation attempts
• Use endpoint protection solutions to monitor for suspicious application behavior