CVE-2021-3612
📋 TL;DR
A local privilege escalation vulnerability in Linux kernel versions before 5.9-rc1 allows attackers with local access to crash systems or gain root privileges through improper bounds checking in joystick device ioctl handling. This affects any Linux system with vulnerable kernel versions and joystick device support. The vulnerability requires local access but can lead to complete system compromise.
💻 Affected Systems
- Linux Kernel
📦 What is this software?
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Fedora by Fedoraproject
Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →⚠️ Risk & Real-World Impact
Worst Case
Local attacker gains root privileges, leading to complete system compromise, data theft, persistence establishment, and lateral movement within the network.
Likely Case
Local user crashes the kernel causing system instability or denial of service, potentially leading to data loss and service disruption.
If Mitigated
With proper access controls and patching, impact is limited to denial of service from crashes, with no privilege escalation possible.
🎯 Exploit Status
Exploit requires local user access. Proof-of-concept code has been published in security advisories and mailing lists.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel 5.9-rc1 and later
Vendor Advisory: https://bugzilla.redhat.com/show_bug.cgi?id=1974079
Restart Required: Yes
Instructions:
1. Update Linux kernel to version 5.9-rc1 or later. 2. For distributions: Use package manager (apt/yum/dnf) to update kernel packages. 3. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable joystick module
linuxPrevent loading of joystick device driver to eliminate attack surface
echo 'blacklist joydev' >> /etc/modprobe.d/blacklist-joystick.conf
rmmod joydev
Restrict ioctl access
linuxUse SELinux/AppArmor to restrict joystick device access
# Configure SELinux/AppArmor policies to deny joystick device access
🧯 If You Can't Patch
- Implement strict access controls to limit local user accounts and monitor for suspicious activity
- Use mandatory access control systems (SELinux/AppArmor) to restrict device access and contain potential exploits
🔍 How to Verify
Check if Vulnerable:
Check kernel version: uname -r. If version is earlier than 5.9-rc1, system is vulnerable.Check Version:
uname -rVerify Fix Applied:
After patching, verify kernel version is 5.9-rc1 or later with uname -r and check that system remains stable during joystick device operations.📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- System crash dumps
- Unusual joystick device access in audit logs
Network Indicators:
- None - local exploit only
SIEM Query:
source="kernel" AND ("panic" OR "oops") AND "joydev" OR source="audit" AND "ioctl" AND "JSIOCSBTNMAP"🔗 References
- https://bugzilla.redhat.com/show_bug.cgi?id=1974079
- https://lists.debian.org/debian-lts-announce/2021/10/msg00010.html
- https://lists.debian.org/debian-lts-announce/2021/12/msg00012.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YKGI562LFV5MESTMVTCG5RORSBT6NGBN/
- https://lore.kernel.org/linux-input/20210620120030.1513655-1-avlarkin82%40gmail.com/
- https://security.netapp.com/advisory/ntap-20210805-0005/
- https://www.oracle.com/security-alerts/cpujul2022.html
- https://bugzilla.redhat.com/show_bug.cgi?id=1974079
- https://lists.debian.org/debian-lts-announce/2021/10/msg00010.html
- https://lists.debian.org/debian-lts-announce/2021/12/msg00012.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YKGI562LFV5MESTMVTCG5RORSBT6NGBN/
- https://lore.kernel.org/linux-input/20210620120030.1513655-1-avlarkin82%40gmail.com/
- https://security.netapp.com/advisory/ntap-20210805-0005/
- https://www.oracle.com/security-alerts/cpujul2022.html
