CVE-2021-29256
📋 TL;DR
This vulnerability in the Arm Mali GPU kernel driver allows unprivileged users to access freed memory, potentially leading to information disclosure or privilege escalation to root. It affects devices using specific versions of Bifrost, Valhall, and Midgard GPU architectures. This impacts Android devices, embedded systems, and other platforms using these Arm Mali GPU drivers.
💻 Affected Systems
- Arm Mali GPU kernel driver
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
An attacker gains root privileges on the device, enabling complete system compromise, data theft, and persistent backdoor installation.
Likely Case
Information disclosure through memory access, potentially exposing sensitive data or cryptographic keys.
If Mitigated
Limited impact if proper kernel hardening and privilege separation are implemented, though memory corruption risks remain.
🎯 Exploit Status
Exploitation requires local access but has been demonstrated in security research. CISA lists it as known exploited.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Bifrost r30p0, Valhall r30p0, Midgard after r30p0
Vendor Advisory: https://developer.arm.com/support/arm-security-updates/mali-gpu-kernel-driver
Restart Required: Yes
Instructions:
1. Check device manufacturer for security updates. 2. Apply GPU driver updates from device vendor. 3. Update to patched kernel versions. 4. Reboot device after update.
🔧 Temporary Workarounds
Restrict GPU access
linuxLimit GPU driver access to trusted users only through SELinux/AppArmor policies
🧯 If You Can't Patch
- Implement strict application sandboxing to limit potential damage
- Monitor for suspicious privilege escalation attempts and kernel module loading
🔍 How to Verify
Check if Vulnerable:
Check GPU driver version: cat /sys/kernel/debug/mali0/version or check device firmware informationCheck Version:
cat /sys/kernel/debug/mali0/version 2>/dev/null || dmesg | grep -i maliVerify Fix Applied:
Verify GPU driver version is r30p0 or later for affected architectures📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages related to Mali driver
- Unexpected privilege escalation attempts
- Suspicious GPU memory access patterns
Network Indicators:
- None - this is a local vulnerability
SIEM Query:
source="kernel" AND ("mali" OR "gpu") AND ("panic" OR "oops" OR "segfault")