CVE-2021-3621
📋 TL;DR
CVE-2021-3621 is a command injection vulnerability in SSSD's sssctl command that allows attackers to execute arbitrary shell commands with root privileges. This occurs when root users run specially crafted sssctl commands via logs-fetch or cache-expire subcommands. Systems using SSSD with vulnerable versions are affected.
💻 Affected Systems
- SSSD (System Security Services Daemon)
📦 What is this software?
Fedora by Fedoraproject
Sssd by Fedoraproject
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with root access, allowing complete control over confidentiality, integrity, and availability.
Likely Case
Privilege escalation to root by tricking administrators into running malicious sssctl commands via sudo or other mechanisms.
If Mitigated
Limited impact if proper access controls restrict who can run sssctl and command arguments are validated.
🎯 Exploit Status
Exploitation requires social engineering or compromised accounts to trick users into running malicious sssctl commands.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: SSSD 2.6.0 and later
Vendor Advisory: https://bugzilla.redhat.com/show_bug.cgi?id=1975142
Restart Required: No
Instructions:
1. Update SSSD to version 2.6.0 or later using your distribution's package manager. 2. For RHEL/CentOS: 'yum update sssd'. 3. For Debian/Ubuntu: 'apt update && apt upgrade sssd'. 4. Verify the update with 'sssd --version'.
🔧 Temporary Workarounds
Restrict sssctl command execution
linuxLimit which users can execute sssctl commands via sudo or other mechanisms
Review and modify sudoers file to restrict sssctl access
Remove sssctl from sudo configurations for non-admin users
Input validation wrapper
linuxCreate a wrapper script that validates sssctl command arguments before execution
Create script that sanitizes input to logs-fetch and cache-expire subcommands
🧯 If You Can't Patch
- Restrict sudo access to sssctl commands to trusted administrators only
- Implement strict input validation for any scripts or tools that call sssctl
🔍 How to Verify
Check if Vulnerable:
Check SSSD version with 'sssd --version' or 'rpm -q sssd' or 'dpkg -l sssd'Check Version:
sssd --versionVerify Fix Applied:
Confirm version is 2.6.0 or later with 'sssd --version'📡 Detection & Monitoring
Log Indicators:
- Unusual sssctl command executions with suspicious arguments
- Shell command execution following sssctl logs-fetch or cache-expire
Network Indicators:
- None - this is a local command injection vulnerability
SIEM Query:
Process execution where command contains 'sssctl' AND (command contains 'logs-fetch' OR command contains 'cache-expire') AND arguments contain shell metacharacters🔗 References
- https://bugzilla.redhat.com/show_bug.cgi?id=1975142
- https://lists.debian.org/debian-lts-announce/2023/05/msg00028.html
- https://sssd.io/release-notes/sssd-2.6.0.html
- https://bugzilla.redhat.com/show_bug.cgi?id=1975142
- https://lists.debian.org/debian-lts-announce/2023/05/msg00028.html
- https://lists.debian.org/debian-lts-announce/2025/02/msg00008.html
- https://sssd.io/release-notes/sssd-2.6.0.html
