CVE-2019-9891
📋 TL;DR
CVE-2019-9891 is a command injection vulnerability in the getopt_simple function from the Advanced Bash Scripting Guide. It allows attackers to escalate privileges and execute arbitrary commands when a vulnerable shell script is executed via sudo or similar privilege escalation mechanisms. This affects any system using shell scripts that implement this specific getopt_simple function.
💻 Affected Systems
- Shell scripts implementing getopt_simple function from Advanced Bash Scripting Guide
📦 What is this software?
⚠️ 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
Full system compromise with root privileges through privilege escalation from a lower-privileged user account.
Likely Case
Local privilege escalation allowing attackers to execute commands with elevated privileges.
If Mitigated
Limited impact if proper sudo configurations restrict script execution and input validation is implemented.
🎯 Exploit Status
Exploitation requires local access and ability to execute or influence vulnerable scripts. Proof of concept available in advisory.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: N/A
Vendor Advisory: https://www.redteam-pentesting.de/advisories/rt-sa-2019-007
Restart Required: No
Instructions:
1. Review all shell scripts for use of getopt_simple function
2. Replace vulnerable function with secure alternatives
3. Update scripts to use proper input validation and sanitization
🔧 Temporary Workarounds
Remove vulnerable function
linuxReplace getopt_simple implementation with secure alternatives like getopts built-in or proper argument parsing libraries
# Replace vulnerable getopt_simple function with secure implementation
# Example using getopts:
while getopts ":a:b:" opt; do
case $opt in
a) arg_a="$OPTARG" ;;
b) arg_b="$OPTARG" ;;
\?) echo "Invalid option: -$OPTARG" >&2 ;;
esac
done
Restrict script execution
linuxModify sudo configurations to restrict execution of vulnerable scripts
# In /etc/sudoers or sudoers.d files
# Restrict specific vulnerable scripts
username ALL=(ALL) !/path/to/vulnerable/script.sh
🧯 If You Can't Patch
- Implement strict input validation and sanitization in all scripts using getopt_simple
- Remove sudo privileges for scripts using vulnerable function and implement alternative privilege management
🔍 How to Verify
Check if Vulnerable:
Search shell scripts for 'getopt_simple' function definition and check if scripts are executed with elevated privileges: grep -r 'getopt_simple' /path/to/scripts/Check Version:
N/A - This is not a packaged software vulnerability but a coding pattern issueVerify Fix Applied:
Verify getopt_simple function has been replaced with secure alternatives and scripts no longer contain vulnerable code: grep -r 'getopt_simple' /path/to/scripts/ should return no results📡 Detection & Monitoring
Log Indicators:
- Unusual command execution patterns from shell scripts
- Failed sudo attempts for specific scripts
- Commands executed with unexpected privileges
Network Indicators:
- N/A - Local privilege escalation
SIEM Query:
source="sudo" AND (command="*getopt_simple*" OR command="*script.sh*")