CVE-2021-47827
📋 TL;DR
CVE-2021-47827 is a denial of service vulnerability in WebSSH for iOS that allows attackers to crash the application by pasting malformed input into the mashREPL tool. This affects iOS users running WebSSH version 14.16.10 who use the mashREPL functionality. The vulnerability can be triggered remotely if the application is exposed to untrusted input sources.
💻 Affected Systems
- WebSSH for iOS
⚠️ 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, potentially disrupting SSH sessions and causing data loss in active connections.
Likely Case
Temporary application crash requiring user to restart WebSSH, interrupting any active SSH sessions.
If Mitigated
Minimal impact if application is not exposed to untrusted input or if input validation is implemented.
🎯 Exploit Status
Exploit requires user to copy and paste malicious content into the application. Proof of concept available in exploit databases.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check App Store for updated version
Vendor Advisory: https://apps.apple.com/mx/app/webssh-ssh-client/id497714887
Restart Required: Yes
Instructions:
1. Open App Store on iOS device
2. Navigate to Updates tab
3. Check for WebSSH update
4. Install available update
5. Restart WebSSH application
🔧 Temporary Workarounds
Disable mashREPL Tool
iosPrevent use of the vulnerable mashREPL component
Input Validation
allImplement client-side input validation for mashREPL field
🧯 If You Can't Patch
- Avoid using mashREPL tool functionality
- Educate users not to paste untrusted content into WebSSH
🔍 How to Verify
Check if Vulnerable:
Check WebSSH version in iOS Settings > General > iPhone Storage > WebSSHCheck Version:
Not applicable for iOS apps - check via App Store or device settingsVerify Fix Applied:
Verify updated version is installed from App Store and test mashREPL with malformed input📡 Detection & Monitoring
Log Indicators:
- Application crash logs showing WebSSH termination
- Unexpected application restarts
Network Indicators:
- Sudden termination of SSH sessions from WebSSH
SIEM Query:
Not typically applicable for mobile application DoS