CVE-2025-21632
📋 TL;DR
A Linux kernel vulnerability in x86 shadow stack ptrace handling allows unprivileged users to trigger a kernel warning (WARN_ON) when attempting to access shadow stack registers via ptrace while shadow stack is disabled. This affects Linux systems with x86 processors supporting Control-flow Enforcement Technology (CET).
💻 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 →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 →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 warning leading to system instability or denial of service through repeated triggering, potentially causing system crashes or performance degradation.
Likely Case
Local denial of service through kernel warnings and potential system instability when users attempt ptrace operations on processes with disabled shadow stacks.
If Mitigated
Minimal impact - kernel warnings logged but system remains operational with proper monitoring and patch management.
🎯 Exploit Status
Exploitation requires local access and ptrace permissions. The vulnerability triggers a warning rather than arbitrary code execution.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in kernel commits: 0a3a872214188e4268d31581ed0cd44508e038cf, 6bfe1fc22f462bec87422cdcbec4d7a2f43ff01d, a9d9c33132d49329ada647e4514d210d15e31d81
Vendor Advisory: https://git.kernel.org/stable/c/0a3a872214188e4268d31581ed0cd44508e038cf
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fix commits. 2. Check distribution-specific security advisories. 3. Reboot system after kernel update.
🔧 Temporary Workarounds
Disable ptrace for untrusted users
linuxRestrict ptrace access to prevent triggering the vulnerability
sysctl -w kernel.yama.ptrace_scope=1
echo 1 > /proc/sys/kernel/yama/ptrace_scope
Disable shadow stack support
linuxTurn off CET shadow stack feature if not required
echo 0 > /proc/sys/kernel/shstk_enabled
🧯 If You Can't Patch
- Implement strict ptrace restrictions using kernel.yama.ptrace_scope
- Monitor kernel logs for WARNING messages related to ssp_get or shadow stack
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if shadow stack is enabled: grep -i shadow /proc/cpuinfo && uname -rCheck Version:
uname -rVerify Fix Applied:
Verify kernel version contains fix commits: grep -E '0a3a872214188e4268d31581ed0cd44508e038cf|6bfe1fc22f462bec87422cdcbec4d7a2f43ff01d|a9d9c33132d49329ada647e4514d210d15e31d81' /proc/version📡 Detection & Monitoring
Log Indicators:
- Kernel WARNING messages containing 'ssp_get' or 'shadow stack'
- dmesg | grep -i 'WARNING.*ssp'
Network Indicators:
- None - local vulnerability only
SIEM Query:
source="kernel" AND "WARNING" AND ("ssp_get" OR "shadow stack")