CVE-2023-53421
📋 TL;DR
A NULL pointer dereference vulnerability in the Linux kernel's block cgroup subsystem can cause kernel panics when resetting block I/O statistics. This affects Linux systems using cgroup v1 with block I/O controllers enabled. The vulnerability allows local attackers to crash the system.
💻 Affected Systems
- Linux kernel
📦 What is this software?
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 →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
Kernel panic leading to system crash and denial of service, potentially causing data loss or service disruption.
Likely Case
Local denial of service through system crash when privileged users or processes trigger the vulnerable code path.
If Mitigated
Limited impact with proper access controls preventing unprivileged users from accessing block cgroup statistics.
🎯 Exploit Status
Exploitation requires local access and ability to trigger blkcg_reset_stats() function, typically requiring appropriate privileges.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in kernel commits: 0561aa6033dd, 3d2af77e31ad, 892faa76be89, abbce7f82613, b0d26283af61
Vendor Advisory: https://git.kernel.org/stable/c/0561aa6033dd181594116d705c41fc16e97161a2
Restart Required: Yes
Instructions:
1. Update to a kernel version containing the fix commits. 2. Check your distribution's security advisories for backported patches. 3. Reboot the system after kernel update.
🔧 Temporary Workarounds
Disable block I/O cgroup controller
linuxPrevent exploitation by disabling the vulnerable subsystem
echo 'blkio' > /sys/fs/cgroup/cgroup.subtree_control
Migrate to cgroup v2
linuxSwitch to cgroup v2 which is not affected by this vulnerability
Add 'systemd.unified_cgroup_hierarchy=1' to kernel boot parameters
🧯 If You Can't Patch
- Restrict access to block cgroup statistics to trusted users only
- Monitor system logs for kernel panic events and implement crash recovery procedures
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if using cgroup v1 with blkio controller: uname -r && cat /proc/cgroups | grep blkioCheck Version:
uname -rVerify Fix Applied:
Verify kernel version includes fix commits: uname -r && check distribution patch notes📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages in /var/log/messages or dmesg
- NULL pointer dereference errors mentioning blkcg_reset_stats
Network Indicators:
- None - local vulnerability only
SIEM Query:
source="kernel" AND ("panic" OR "NULL pointer dereference") AND "blkcg"🔗 References
- https://git.kernel.org/stable/c/0561aa6033dd181594116d705c41fc16e97161a2
- https://git.kernel.org/stable/c/3d2af77e31ade05ff7ccc3658c3635ec1bea0979
- https://git.kernel.org/stable/c/892faa76be894d324bf48b12a55c7af7be2bad83
- https://git.kernel.org/stable/c/abbce7f82613ea5eeefd0fc3c1c8e449b9cef2a2
- https://git.kernel.org/stable/c/b0d26283af612b9e0cc3188b0b88ad7fdea447e8
