CVE-2021-47876
📋 TL;DR
GeoGebra Classic 5.0.631.0-d contains a denial of service vulnerability where attackers can crash the application by pasting extremely large content (800,000 repeated characters) into the 'Entrada:' input field. This affects users of the vulnerable version who open malicious files or receive crafted input. The vulnerability allows disruption of the application but doesn't enable code execution.
💻 Affected Systems
- GeoGebra Classic
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Complete application crash requiring restart, potential data loss if unsaved work is present, and disruption of educational or mathematical workflows.
Likely Case
Application becomes unresponsive and crashes, requiring manual restart and potentially losing unsaved work.
If Mitigated
Minimal impact - application remains stable with proper input validation or updated version.
🎯 Exploit Status
Exploit requires user interaction (pasting content) but is trivial to execute once the malicious content is prepared.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after 5.0.631.0-d
Vendor Advisory: https://www.geogebra.org
Restart Required: Yes
Instructions:
1. Open GeoGebra Classic. 2. Go to Help > Check for Updates. 3. Follow prompts to install latest version. 4. Restart application.
🔧 Temporary Workarounds
Input Validation Script
allMonitor clipboard content length before pasting into GeoGebra
# No direct command - requires custom script to check clipboard size
Application Sandboxing
allRun GeoGebra in restricted environment to limit impact of crashes
# Platform-specific sandboxing commands would vary
🧯 If You Can't Patch
- Educate users not to paste untrusted content into GeoGebra input fields
- Implement application whitelisting to prevent execution of vulnerable version
🔍 How to Verify
Check if Vulnerable:
Check GeoGebra version in Help > About. If version is exactly 5.0.631.0-d, it's vulnerable.Check Version:
On Linux: geogebra --version; On Windows: Check Help > About in applicationVerify Fix Applied:
Update to latest version and attempt to paste 800,000 character string - application should handle input without crashing.📡 Detection & Monitoring
Log Indicators:
- Application crash logs
- Unexpected termination events
- Large memory allocation failures
Network Indicators:
- Not applicable - local vulnerability
SIEM Query:
EventID=1000 OR EventID=1001 AND ProcessName="GeoGebra.exe" AND Version="5.0.631.0-d"