CVE-2021-47875: GeoGebra CAS Calculator DoS Vulnerability

CVE-2021-47875 Overview

GeoGebra CAS Calculator version 6.0.631.0 contains a denial of service vulnerability caused by improper resource allocation handling. Attackers can crash the application by generating a large buffer overflow through specially crafted input. The vulnerability is triggered when a payload containing 8000 or more repeated characters is pasted into the calculator's input field, resulting in complete application failure.

Critical Impact

Successful exploitation allows attackers to crash the GeoGebra CAS Calculator application, causing denial of service for users relying on the tool for mathematical computations and educational purposes.

Affected Products

• GeoGebra CAS Calculator 6.0.631.0

Discovery Timeline

• 2026-01-21 - CVE CVE-2021-47875 published to NVD
• 2026-01-21 - Last updated in NVD database

Technical Details for CVE-2021-47875

Vulnerability Analysis

This vulnerability stems from improper handling of resource allocation (CWE-770: Allocation of Resources Without Limits or Throttling) within the GeoGebra CAS Calculator application. The application fails to implement adequate input length validation on user-supplied data, allowing excessively long strings to be processed without restriction.

When a user pastes an extremely long string (approximately 8000 characters or more) into the calculator's input field, the application attempts to allocate memory and process this input without proper bounds checking. This leads to a buffer overflow condition that overwhelms the application's memory handling capabilities, resulting in an unrecoverable 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 content into the application. While the vulnerability does not result in data disclosure or system compromise, it effectively renders the application unusable until restarted.

Root Cause

The root cause is a failure to implement proper input validation and resource allocation limits within the GeoGebra CAS Calculator's input handling routines. The application does not enforce maximum input length restrictions, allowing unbounded memory allocation requests that exceed available resources or buffer sizes.

Attack Vector

The attack requires local access to the application and user interaction to execute. An attacker can exploit this vulnerability by:

1. Creating a payload consisting of 8000+ repeated characters
2. Copying this payload to the clipboard
3. Pasting the payload into the GeoGebra CAS Calculator input field
4. The application crashes due to the buffer overflow condition

The vulnerability does not require special privileges and can be triggered by any user with access to the application. Additional technical details can be found in the Exploit-DB entry #49655 and the VulnCheck Advisory.

Detection Methods for CVE-2021-47875

Indicators of Compromise

• Repeated application crashes of GeoGebra.exe or related processes
• Memory allocation errors in application event logs
• Unexplained high memory usage spikes before application termination
• User reports of calculator freezing when pasting content

Detection Strategies

• Monitor for abnormal process termination events related to GeoGebra CAS Calculator
• Implement endpoint detection rules for applications crashing due to memory exhaustion
• Configure application crash reporting to alert on repeated GeoGebra failures
• Review system event logs for buffer overflow or memory allocation errors

Monitoring Recommendations

• Enable crash dump collection for forensic analysis of application failures
• Deploy SentinelOne endpoint protection to detect and prevent resource exhaustion attacks
• Implement user education programs to raise awareness about pasting content from untrusted sources
• Configure system monitoring to track application stability metrics

How to Mitigate CVE-2021-47875

Immediate Actions Required

• Upgrade GeoGebra CAS Calculator to the latest available version from GeoGebra's official website
• Educate users about the risks of pasting content from untrusted sources into the application
• Consider using the web-based version of GeoGebra which may have different input handling
• Implement application control policies to manage GeoGebra deployments in enterprise environments

Patch Information

Users should check the GeoGebra official website for the latest version of the CAS Calculator that addresses this vulnerability. It is recommended to update from version 6.0.631.0 to the most recent stable release that includes input validation improvements.

Workarounds

• Restrict copy-paste functionality when using GeoGebra CAS Calculator with untrusted data
• Manually validate input length before pasting into the application
• Use application sandboxing to limit the impact of crashes on the host system
• Deploy endpoint protection solutions that can detect and prevent denial of service conditions