Samsung Android sec_log Kernel Information Disclosure Vulnerability Analysis (CVE-2021-25369)
Executive & SecOps Summary
SECOPS ASSESSMENTSamsung Android devices prior to SMR (Samsung Maintenance Release) March 2021 Release 1
Local attackers can bypass critical kernel protections like KASLR by reading sensitive kernel memory addresses and structures from the improperly secured sec_log file
Apply the official Samsung SMR March 2021 Release 1 (or later) firmware update immediately, or restrict access permissions to the debug log node
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
The primary remediation is to update the device firmware to the latest version via Over-The-Air (OTA) updates. In enterprise environments, enforce this update using Mobile Device Management (MDM) solutions.
# Verify the current security patch level of the device via ADB
adb shell getprop ro.build.version.security_patch
# Ensure the returned patch date is 2021-03-01 or later.2. Temporary Workaround & Hardening Configuration
For legacy or development devices where immediate patching is not feasible, you can temporarily restrict access to the sec_log device node using ADB (requires root privileges).
# Restrict read/write permissions of the sec_log device file to root only
adb shell 'su -c "chmod 600 /dev/sec_log"'
# Verify the updated permissions (should display rw-------)
adb shell 'su -c "ls -l /dev/sec_log"'3. Log Audit & IoC Verification Commands
To audit whether unauthorized processes have attempted to access the sec_log file, run the following logcat analysis command.
# Filter logcat for unauthorized access attempts or permission errors related to sec_log
adb logcat -d | grep -E 'sec_log|Permission denied'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-2021-25369) is an improper access control flaw (CWE-200) residing in the sec_log driver file of Samsung Android devices. The sec_log node, which records kernel-level debug information and system logs, was designed with insufficient permission restrictions, allowing unprivileged userspace processes to read its contents directly.
2. Exploitation Mechanics & Attack Scenario
A local attacker or a malicious application installed on the device can read data from /dev/sec_log or associated virtual file system nodes without requiring elevated privileges. This log file exposes sensitive kernel internal information, such as kernel function pointers, stack addresses, and physical memory maps in plaintext. Attackers leverage this information to defeat Kernel Address Space Layout Randomization (KASLR), facilitating subsequent local privilege escalation (LPE) exploits.
3. Infrastructure & Business Impact
This vulnerability is highly critical and is actively exploited in the wild, as evidenced by its inclusion in the CISA Known Exploited Vulnerabilities (KEV) catalog. In an enterprise environment, if an employee's mobile device is compromised via this flaw, it can lead to full root access, corporate data exfiltration, and the compromise of multi-factor authentication (MFA) tokens.
Official Vendor Advisories & References
An improper access control vulnerability in sec_log file prior to SMR MAR-2021 Release 1 exposes sensitive kernel information to userspace.
Frequently Asked SecOps Questions (CVE-2021-25369)
FAQQ1. How critical is CVE-2021-25369 and is it actively exploited in the wild?
CVE-2021-25369 is rated CVSS 5.5 (MEDIUM) with a 30-day EPSS exploitation probability of 1.1%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2021-25369?
Primary impacted vendors include samsung across android, sec_log. Scope summary: All Samsung Android smartphones and tablets running firmware versions prior to SMR MAR-2021 Release 1
Q3. What temporary mitigations or workarounds exist for CVE-2021-25369 before patching?
[Mitigation] Apply the official Samsung SMR March 2021 Release 1 (or later) firmware update immediately, or restrict access permissions to the debug log node Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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