CVE-2018-16494
📋 TL;DR
This vulnerability in Versa Operating System (VOS) uses an overly permissive umask setting, allowing authorized users to access files and directories with insecure permissions. This can lead to unauthorized reading, writing, or execution of newly created files. Affected systems include Versa servers running vulnerable VOS versions.
💻 Affected Systems
- Versa Operating System (VOS)
📦 What is this software?
Versa Operating System by Versa Networks
Versa Operating System by Versa Networks
Versa Operating System by Versa Networks
⚠️ Risk & Real-World Impact
Worst Case
Authorized users could escalate privileges to root/admin, execute arbitrary code, read sensitive configuration files, or modify system files leading to complete system compromise.
Likely Case
Authorized users could read sensitive data, modify application files, or execute unauthorized commands within their privilege level.
If Mitigated
With proper file permission controls and monitoring, impact would be limited to unauthorized file access within user's existing privilege scope.
🎯 Exploit Status
Exploitation requires authorized user access. Attackers with valid credentials can leverage the insecure umask to access files they shouldn't be able to.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified in CVE details
Vendor Advisory: https://hackerone.com/reports/1168191
Restart Required: Yes
Instructions:
1. Contact Versa Networks for the specific patch version. 2. Apply the official patch from Versa. 3. Restart affected services/servers. 4. Verify the umask settings have been corrected.
🔧 Temporary Workarounds
Manual umask correction
linuxManually set secure umask values in system configuration
echo "umask 0027" >> /etc/profile
echo "umask 0027" >> /etc/bashrc
source /etc/profile
File permission hardening
linuxReview and correct permissions on sensitive directories and files
find / -type f -perm /o+rwx -exec chmod o-rwx {} \;
find / -type d -perm /o+rwx -exec chmod o-rwx {} \;
🧯 If You Can't Patch
- Implement strict access controls and least privilege principles for all user accounts
- Deploy file integrity monitoring to detect unauthorized file modifications
🔍 How to Verify
Check if Vulnerable:
Check current umask setting: run 'umask' command. If output is less restrictive than 0027 (e.g., 0002, 0022), system may be vulnerable.Check Version:
Contact Versa support or check system documentation for VOS versionVerify Fix Applied:
Verify umask shows 0027 or more restrictive. Check that newly created files have secure permissions (e.g., -rw-r----- for files, drwxr-x--- for directories).📡 Detection & Monitoring
Log Indicators:
- Unexpected file permission changes
- Unauthorized file access attempts
- User creating files with insecure permissions
Network Indicators:
- Unusual file transfer patterns from authorized users
- Unexpected outbound connections following file access
SIEM Query:
source="system_logs" (event="file_permission_change" OR event="file_access") AND (user="authorized_user") AND (permission="world_readable" OR permission="world_writable")