CVE-2023-53621
📋 TL;DR
A race condition in the Linux kernel's memory controller (memcontrol) subsystem can cause a NULL pointer dereference when retrieving memory cgroups by ID. This vulnerability allows local attackers to trigger a kernel panic (denial of service) on affected systems. Any system running an unpatched Linux kernel with memory cgroups enabled is potentially affected.
💻 Affected Systems
- Linux kernel
⚠️ Risk & Real-World Impact
Worst Case
Local attacker triggers kernel panic leading to system crash and denial of service, potentially causing data loss or service disruption.
Likely Case
Local user or process triggers kernel panic resulting in system crash and temporary denial of service.
If Mitigated
System remains stable with no impact if patched or if memory cgroups are disabled.
🎯 Exploit Status
Exploitation requires local access and specific timing conditions to trigger the race condition. No public exploit code identified in references.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in kernel commits 6f0df8e16eb543167f2929cb756e695709a3551d and b9d30c38ee859d833a51131b5b4b864c7a6219d0
Vendor Advisory: https://git.kernel.org/stable/c/6f0df8e16eb543167f2929cb756e695709a3551d
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fix commits. 2. Check with your distribution vendor for patched kernel packages. 3. Reboot system after kernel update.
🔧 Temporary Workarounds
Disable memory cgroups
linuxDisable memory cgroups subsystem to prevent exploitation (may impact containerization and resource management)
Add 'cgroup_disable=memory' to kernel boot parameters in GRUB configuration
🧯 If You Can't Patch
- Restrict local user access to prevent untrusted users from running code on the system
- Implement strict process isolation and resource limits to reduce attack surface
🔍 How to Verify
Check if Vulnerable:
Check kernel version and verify if memory cgroups are enabled: cat /proc/cmdline | grep -i cgroupCheck Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits or check with distribution vendor for patched kernel version📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs with NULL pointer dereference at mem_cgroup_get_nr_swap_pages
- System crash/reboot events
Network Indicators:
- None - local exploitation only
SIEM Query:
Search for kernel panic events or system crash logs with mem_cgroup_get_nr_swap_pages in stack trace