CVE-2021-4459
📋 TL;DR
CVE-2021-4459 is a path traversal vulnerability in Sunny Boy devices that allows authorized remote attackers to access files and directories outside the intended web root. This could expose sensitive system information, configuration files, or credentials. The vulnerability affects SMA Solar Technology Sunny Boy devices with web interfaces.
💻 Affected Systems
- SMA Solar Technology Sunny Boy devices
⚠️ 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
Attackers could access sensitive system files, configuration data, or credentials, potentially leading to full device compromise, data exfiltration, or lateral movement within the network.
Likely Case
Attackers with valid credentials could enumerate directory structures and access files containing device configuration, logs, or other sensitive information.
If Mitigated
With proper access controls and network segmentation, impact is limited to information disclosure within the compromised device's filesystem.
🎯 Exploit Status
Exploitation requires valid credentials but uses standard path traversal techniques
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware versions released after 2021
Vendor Advisory: https://certvde.com/en/advisories/VDE-2025-066
Restart Required: Yes
Instructions:
1. Check current firmware version. 2. Download latest firmware from SMA Solar Technology portal. 3. Apply firmware update following vendor instructions. 4. Verify update completed successfully.
🔧 Temporary Workarounds
Network Segmentation
allIsolate Sunny Boy devices from untrusted networks and restrict access to authorized management systems only
Access Control Hardening
allImplement strong authentication mechanisms and limit user privileges to minimum necessary
🧯 If You Can't Patch
- Implement strict network access controls to limit device exposure
- Monitor device logs for unusual file access patterns or authentication attempts
🔍 How to Verify
Check if Vulnerable:
Check firmware version against vendor advisory. Test with controlled path traversal attempts if authorized.Check Version:
Check device web interface or use vendor-specific CLI commands for firmware versionVerify Fix Applied:
Verify firmware version is updated to patched version. Test path traversal attempts should fail.📡 Detection & Monitoring
Log Indicators:
- Unusual file access patterns
- Multiple failed authentication attempts followed by successful login
- Requests containing '../' or similar path traversal sequences
Network Indicators:
- Unusual outbound connections from device
- Traffic patterns indicating file enumeration
SIEM Query:
source="sunnyboy" AND (uri="*../*" OR status=200 AND uri="*/etc/*" OR uri="*/config/*")