Samsung Mobile MFC Charger Driver Race Condition Use-After-Free (CVE-2021-25394) Technical Analysis and Hardening Guide
Executive & SecOps Summary
SECOPS ASSESSMENTSamsung mobile devices running firmware versions prior to SMR (Samsung Security Maintenance Release) MAY-2021 Release 1.
A local attacker with compromised radio privileges can trigger a race condition to perform an arbitrary write in kernel memory, leading to local privilege escalation (LPE).
Apply the official Samsung security update (SMR MAY-2021 Release 1 or later) and restrict unauthorized local application execution.
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
The primary remediation is to apply the official Samsung OTA system update. In enterprise environments, enforce the update using Mobile Device Management (MDM) solutions.
# Verify the current security patch level and build ID via ADB
adb shell getprop ro.build.version.security_patch
adb shell getprop ro.build.display.id
# Ensure the patch level is '2021-05-01' or later.2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, minimize the attack surface by disabling sideloading and restricting debugging interfaces.
# Disable installation of applications from unknown sources via ADB
adb shell settings put global install_non_market_apps 0
# Disable network debugging to prevent remote ADB exploitation vectors
adb shell setprop service.adb.tcp.port -13. Log Audit & IoC Verification Commands
Monitor system logs and kernel ring buffers for anomalies or crashes related to the MFC driver that may indicate exploitation attempts.
# Scan system logs for MFC driver crashes or kernel panic signatures
adb logcat -d | grep -Ei 'mfc|charger|use-after-free|general protection fault|kernel panic'Block Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
Protect unpatched Windows, Linux, and macOS workloads against in-memory exploitation and lateral movement with autonomous EDR.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2021-25394) is a Use-After-Free (UAF, CWE-416) flaw caused by a race condition (CWE-362) within the Multi-Function Charger (MFC) driver of Samsung mobile devices. The root cause lies in the lack of proper synchronization primitives (such as mutexes or spinlocks) when managing the lifecycle of driver-specific objects, allowing concurrent threads to access and free the same memory resource simultaneously.
2. Exploitation Mechanics & Attack Scenario
To exploit this vulnerability, an attacker must first compromise a process with radio privileges on the target device. The attacker then initiates highly-timed concurrent threads targeting the MFC charger driver's file descriptors (e.g., via ioctl calls). By racing these threads, the attacker forces one thread to free an object while another thread is still referencing it. By reclaiming the freed memory chunk with controlled payload data (heap spraying), the attacker can overwrite kernel pointers, achieve arbitrary write capabilities, and escalate privileges to root.
3. Infrastructure & Business Impact
As this vulnerability is actively exploited in the wild and listed in the CISA KEV catalog, it poses a severe threat to enterprise mobile security. Successful exploitation allows complete compromise of the device's operating system, enabling attackers to bypass containerization (e.g., Knox), exfiltrate sensitive corporate data, and establish persistent access within the enterprise network.
Official Vendor Advisories & References
A use after free vulnerability via race condition in MFC charger driver prior to SMR MAY-2021 Release 1 allows arbitrary write given a radio privilege is compromised.
Frequently Asked SecOps Questions (CVE-2021-25394)
FAQQ1. How critical is CVE-2021-25394 and is it actively exploited in the wild?
CVE-2021-25394 is rated CVSS 6.4 (MEDIUM) with a 30-day EPSS exploitation probability of 0.4%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2021-25394?
Primary impacted vendors include samsung across mfc charger driver, android. Scope summary: Samsung Android mobile devices running firmware versions prior to SMR MAY-2021 Release 1
Q3. What temporary mitigations or workarounds exist for CVE-2021-25394 before patching?
[Mitigation] Apply the official Samsung security update (SMR MAY-2021 Release 1 or later) and restrict unauthorized local application execution. Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
Generate an Internal Engineering Notice or CISO Report for CVE-2021-25394
Instantly format this advisory into an executive CISO summary or engineering patch ticket.
🔗 Related Advisories in Similar Stack (samsung)
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