CVE-2020-25669
📋 TL;DR
This CVE describes a use-after-free vulnerability in the Linux kernel's Sun keyboard driver (sunkbd). An attacker with local access can potentially exploit this to cause a kernel crash (denial of service) or execute arbitrary code with kernel privileges. All Linux systems using the affected kernel versions are vulnerable if the Sun keyboard driver is loaded.
💻 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 →Solidfire \& Hci Management Node by Netapp
⚠️ Risk & Real-World Impact
Worst Case
Local privilege escalation to root/kernel level, allowing complete system compromise and potential persistence.
Likely Case
Kernel panic leading to system crash and denial of service, requiring physical or remote console access to reboot.
If Mitigated
No impact if the Sun keyboard driver is not loaded or if proper access controls prevent local user exploitation.
🎯 Exploit Status
Exploitation requires precise timing to trigger the use-after-free condition between interrupt scheduling and driver disconnection. No public exploits have been documented.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel v5.10-rc1 and later, backported to stable branches
Vendor Advisory: https://lists.debian.org/debian-lts-announce/2020/12/msg00015.html
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing commit 77e70d351db7de07a46ac49b87a6c3c7a60fca7e. 2. For distributions: Use package manager (apt/yum/dnf) to install latest kernel updates. 3. Reboot system to load patched kernel.
🔧 Temporary Workarounds
Unload Sun keyboard driver
linuxPrevent exploitation by unloading the vulnerable sunkbd kernel module if not needed
sudo rmmod sunkbd
Blacklist driver module
linuxPrevent automatic loading of the vulnerable driver
echo 'blacklist sunkbd' | sudo tee /etc/modprobe.d/blacklist-sunkbd.conf
sudo update-initramfs -u
🧯 If You Can't Patch
- Restrict local user access to systems where Sun keyboard driver is loaded
- Implement strict privilege separation and limit user capabilities to reduce attack surface
🔍 How to Verify
Check if Vulnerable:
Check if sunkbd module is loaded: lsmod | grep sunkbd. If loaded and kernel version is before v5.10-rc1, system is vulnerable.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes fix: grep -q '77e70d351db7de07a46ac49b87a6c3c7a60fca7e' /boot/config-$(uname -r) 2>/dev/null && echo 'Patched' || echo 'Check kernel source'📡 Detection & Monitoring
Log Indicators:
- Kernel oops messages related to sunkbd driver
- System crashes/panics with sunkbd in stack trace
Network Indicators:
- None - local exploitation only
SIEM Query:
source="kernel" AND ("sunkbd" OR "use-after-free")🔗 References
- http://www.openwall.com/lists/oss-security/2020/11/05/2
- http://www.openwall.com/lists/oss-security/2020/11/20/5
- https://github.com/torvalds/linux/commit/77e70d351db7de07a46ac49b87a6c3c7a60fca7e
- https://lists.debian.org/debian-lts-announce/2020/12/msg00015.html
- https://lists.debian.org/debian-lts-announce/2020/12/msg00027.html
- https://security.netapp.com/advisory/ntap-20210702-0006/
- https://www.openwall.com/lists/oss-security/2020/11/05/2%2C
- https://www.openwall.com/lists/oss-security/2020/11/20/5%2C
- http://www.openwall.com/lists/oss-security/2020/11/05/2
- http://www.openwall.com/lists/oss-security/2020/11/20/5
- https://github.com/torvalds/linux/commit/77e70d351db7de07a46ac49b87a6c3c7a60fca7e
- https://lists.debian.org/debian-lts-announce/2020/12/msg00015.html
- https://lists.debian.org/debian-lts-announce/2020/12/msg00027.html
- https://security.netapp.com/advisory/ntap-20210702-0006/
- https://www.openwall.com/lists/oss-security/2020/11/05/2%2C
- https://www.openwall.com/lists/oss-security/2020/11/20/5%2C
