Samsung Mobile MFC Charger Driver Race Condition Vulnerability (CVE-2021-25395) Technical Advisory
Executive & SecOps Summary
SECOPS ASSESSMENTSamsung mobile devices running firmware versions prior to SMR (Security Maintenance Release) MAY-2021 Release 1
Local attackers with compromised radio privileges can bypass signature checks via a race condition, leading to arbitrary code execution in the kernel context
Apply the official Samsung security update (SMR MAY-2021 Release 1 or later) immediately and restrict unauthorized application installation
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
The primary remediation is to upgrade the device firmware to SMR MAY-2021 Release 1 or later. For enterprise environments, enforce system updates via MDM policies or trigger update checks using ADB commands.
# Force trigger system update check via ADB (for testing/management)
adb shell cmd jobscheduler run-jobs --namespace android.system.update2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, restrict the installation of applications requesting radio or system-level privileges. Disable unused system packages that possess high-privilege access.
# Disable potentially compromised or unused high-privilege system packages
adb shell pm disable-user --user 0 com.samsung.android.radio3. Log Audit & IoC Verification Commands
Use the following shell script to verify the current Android Security Patch Level of connected devices to determine vulnerability status.
# Retrieve and verify the security patch level of the connected Android device
PATCH_LEVEL=$(adb shell getprop ro.build.version.security_patch)
echo 'Current Security Patch Level:' $PATCH_LEVEL
# Compare patch level with the fixed release date (2021-05-01)
if [ '$(date -d $PATCH_LEVEL +%s)' -lt '$(date -d '2021-05-01' +%s)' ]; then
echo '[WARNING] Device is VULNERABLE to CVE-2021-25395. Immediate update required.'
else
echo '[INFO] Device is secure against CVE-2021-25395.'
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Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2021-25395) is a race condition (CWE-362) discovered in 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 handling state transitions or resource allocation within the driver, allowing concurrent threads to access shared resources in an unsynchronized manner.
2. Exploitation Mechanics & Attack Scenario
To exploit this vulnerability, an attacker must first obtain local execution capabilities with elevated 'radio' privileges on the target device. Once this prerequisite is met, the attacker can initiate multiple concurrent requests to the MFC charger driver's ioctl interface. By winning the race condition, the attacker can bypass the driver's signature verification routine, allowing the loading or execution of unsigned, malicious payloads directly within the kernel space.
3. Infrastructure & Business Impact
As this vulnerability is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, it represents a highly active threat vector. Successful exploitation leads to Local Privilege Escalation (LPE) to kernel-level privileges, completely compromising the device's integrity. In an enterprise environment, compromised mobile endpoints can serve as initial access vectors to pivot into internal corporate networks and exfiltrate sensitive data.
Official Vendor Advisories & References
A race condition in MFC charger driver prior to SMR MAY-2021 Release 1 allows local attackers to bypass signature check given a radio privilege is compromised.
Frequently Asked SecOps Questions (CVE-2021-25395)
FAQQ1. How critical is CVE-2021-25395 and is it actively exploited in the wild?
CVE-2021-25395 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-2021-25395?
Primary impacted vendors include samsung across mfc charger driver, android. Scope summary: Samsung Android mobile devices with firmware releases prior to SMR MAY-2021 Release 1
Q3. What temporary mitigations or workarounds exist for CVE-2021-25395 before patching?
[Mitigation] Apply the official Samsung security update (SMR MAY-2021 Release 1 or later) immediately and restrict unauthorized application installation Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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