CVE-2021-47063
📋 TL;DR
This CVE describes a use-after-free vulnerability in the Linux kernel's DRM (Direct Rendering Manager) subsystem. When a bridge is detached from a panel, the connector object isn't properly cleaned up, leading to potential memory corruption. This affects systems using the Linux kernel with DRM graphics drivers.
💻 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
Kernel panic, system crash, or potential privilege escalation leading to full system compromise.
Likely Case
System instability, crashes, or denial of service affecting graphical functionality.
If Mitigated
Minimal impact with proper kernel hardening and isolation mechanisms in place.
🎯 Exploit Status
Requires local access and knowledge of DRM subsystem to trigger the use-after-free condition.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Multiple stable kernel versions with fixes available (see git commit references)
Vendor Advisory: https://git.kernel.org/stable/c/18149b420c9bd93c443e8d1f48a063d71d9f6aa1
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version. 2. Check distribution-specific security advisories. 3. Reboot system after kernel update.
🔧 Temporary Workarounds
Disable affected DRM functionality
linuxDisable panel bridge functionality if not required
echo 'blacklist drm_panel_bridge' > /etc/modprobe.d/disable-drm-panel-bridge.conf
update-initramfs -u
🧯 If You Can't Patch
- Restrict local user access to systems with vulnerable kernels
- Implement kernel hardening features like KASLR and strict memory protections
🔍 How to Verify
Check if Vulnerable:
Check kernel version and compare with patched versions in git commitsCheck Version:
uname -rVerify Fix Applied:
Verify kernel version is updated to include the fix commits📡 Detection & Monitoring
Log Indicators:
- Kernel oops messages
- DRM subsystem errors in dmesg
- System crash logs
Network Indicators:
- None - local vulnerability only
SIEM Query:
source="kernel" AND ("drm" OR "panel_bridge" OR "use-after-free")🔗 References
- https://git.kernel.org/stable/c/18149b420c9bd93c443e8d1f48a063d71d9f6aa1
- https://git.kernel.org/stable/c/4d906839d321c2efbf3fed4bc31ffd9ff55b75c0
- https://git.kernel.org/stable/c/98d7d76a74e48ec3ddf2e23950adff7edcab9327
- https://git.kernel.org/stable/c/ce450934a00cf896e648fde08d0bd1426653d7a2
- https://git.kernel.org/stable/c/18149b420c9bd93c443e8d1f48a063d71d9f6aa1
- https://git.kernel.org/stable/c/4d906839d321c2efbf3fed4bc31ffd9ff55b75c0
- https://git.kernel.org/stable/c/98d7d76a74e48ec3ddf2e23950adff7edcab9327
- https://git.kernel.org/stable/c/ce450934a00cf896e648fde08d0bd1426653d7a2
