CVE-2023-52831
📋 TL;DR
A Linux kernel vulnerability where attempting to offline the last non-isolated CPU on systems with isolated CPUs causes a kernel panic. This affects Linux systems using CPU isolation via the 'isolcpus' kernel parameter, potentially leading to system crashes during CPU hotplug operations.
💻 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 →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
System crash and denial of service requiring physical reboot, potentially causing data loss or service disruption.
Likely Case
System crash during legitimate CPU hotplug operations on systems with isolated CPUs configured.
If Mitigated
No impact if systems don't use CPU isolation or avoid CPU hotplug operations.
🎯 Exploit Status
Requires ability to trigger CPU hotplug operations, typically requiring privileged access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Multiple stable kernel versions with fixes (see git commits in references)
Vendor Advisory: https://git.kernel.org/stable/c/3073f6df783d9d75f7f69f73e16c7ef85d6cfb63
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version. 2. Check distribution-specific advisories. 3. Reboot system after kernel update.
🔧 Temporary Workarounds
Avoid CPU hotplug operations
linuxPrevent triggering the vulnerability by avoiding CPU offline operations
Remove CPU isolation
linuxRemove 'isolcpus' kernel parameter if not required
Edit /etc/default/grub or bootloader config to remove 'isolcpus=' parameter
Run 'update-grub' or equivalent
Reboot system
🧯 If You Can't Patch
- Avoid using CPU isolation via 'isolcpus' parameter
- Implement strict access controls to prevent unauthorized CPU hotplug operations
🔍 How to Verify
Check if Vulnerable:
Check if 'isolcpus' is in kernel command line: cat /proc/cmdline | grep isolcpusCheck Version:
uname -rVerify Fix Applied:
Check kernel version against patched versions from git commits, verify 'isolcpus' parameter still works without crashes📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs with WARNING about build_sched_domains
- CPU hotplug operation failures
- System crash/reboot events
Network Indicators:
- Sudden loss of connectivity to system
SIEM Query:
event_type:"kernel" AND (message:"WARNING.*build_sched_domains" OR message:"partition_sched_domains_locked")🔗 References
- https://git.kernel.org/stable/c/3073f6df783d9d75f7f69f73e16c7ef85d6cfb63
- https://git.kernel.org/stable/c/335a47ed71e332c82339d1aec0c7f6caccfcda13
- https://git.kernel.org/stable/c/3410b702354702b500bde10e3cc1f9db8731d908
- https://git.kernel.org/stable/c/38685e2a0476127db766f81b1c06019ddc4c9ffa
- https://git.kernel.org/stable/c/3073f6df783d9d75f7f69f73e16c7ef85d6cfb63
- https://git.kernel.org/stable/c/335a47ed71e332c82339d1aec0c7f6caccfcda13
- https://git.kernel.org/stable/c/3410b702354702b500bde10e3cc1f9db8731d908
- https://git.kernel.org/stable/c/38685e2a0476127db766f81b1c06019ddc4c9ffa
