CVE-2021-25394: Samsung Mobile Devices Race Condition Vulnerability

CVE-2021-25394 is a race condition vulnerability in the MFC charger driver on Samsung mobile devices. When a radio privilege is already compromised, the flaw can lead to a use-after-free condition that permits a write operation. For IT and security teams managing fleets of Samsung handsets or tablets, this matters because it can enable further privilege escalation or code execution once an attacker has limited radio-level access, expanding the impact of an initial compromise.

Public detail is limited to the CISA description; exact affected models, firmware builds, and exploitation requirements must be confirmed against the vendor advisory. Known ransomware use is not documented.

How it works

The underlying weakness is CWE-416 (use-after-free), reached via a race condition inside the MFC charger driver. A race condition occurs when the timing or ordering of concurrent operations is not properly synchronized, allowing an attacker who already holds radio privilege to free a memory object while another code path still holds a reference to it. Subsequent use of that dangling reference can corrupt memory and enable an arbitrary write.

In practical terms, once radio privilege is obtained (for example through a separate vulnerability or malicious baseband interaction), the attacker can race the charger driver’s resource handling to trigger the use-after-free. The resulting write capability can be leveraged to alter kernel structures or escalate further. No public exploit code or precise trigger sequence is provided in the available facts; defenders should treat the class of race-to-use-after-free in kernel drivers as high-impact once the prerequisite privilege is present.

Am I affected? How to find it in your systems

The vulnerability affects Samsung mobile devices that include the MFC charger driver. These devices are commonly found as corporate-issued smartphones and tablets running Samsung’s Android-based firmware.

• Inventory all Samsung handsets and tablets via MDM, EMM, or asset-management tools; record model numbers and current firmware/security-patch levels.
• Compare those firmware versions against the vendor advisory for CVE-2021-25394; only the advisory lists the precise builds that contain the fix.
• Where MDM telemetry is available, look for unexpected radio-privilege processes, anomalous charger-driver interactions, or kernel oops/panic logs that mention MFC or use-after-free patterns. Such signs are not definitive of exploitation but warrant investigation.
• Confirm whether devices are enrolled in automatic security updates; unmanaged or personally owned devices used for work may still be exposed.

Because version details are not supplied here, treat any Samsung mobile device whose security patch level predates the vendor’s fix as potentially affected until verified.

How to remediate

The primary remediation is to apply the updates published by Samsung according to the vendor instructions for CVE-2021-25394. CISA’s required action is to apply those updates or discontinue use of the product if updates are unavailable.

• Push the relevant firmware or security-patch package through your MDM/EMM as soon as it is available for each model.
• Verify successful installation by checking the device’s security-patch level against the advisory.
• For devices that cannot receive the update, retire or isolate them from sensitive networks and data.
• After patching, re-baseline kernel and driver integrity checks so that any residual memory-corruption artifacts can be detected.

Hardening for this class of kernel race condition also includes enforcing least-privilege radio access, keeping baseband firmware current, and enabling any vendor-supplied exploit-mitigation features (for example, memory tagging or control-flow integrity) once confirmed present in the patched build.

If you can't patch immediately

Until the vendor update can be applied, reduce exposure with compensating controls:

• Segment affected devices onto restricted network segments that limit radio and data connectivity to only essential services.
• Disable or tightly control features that interact with the charger driver or radio stack if the vendor provides such configuration options; confirm availability in the device settings or MDM policies.
• Deploy virtual patching or host-based monitoring that watches for anomalous memory-access patterns or unexpected privilege transitions involving radio processes.
• Increase logging of kernel events, charger-driver activity, and radio-privilege changes; forward these logs to a SIEM for correlation with other indicators of compromise.
• If the device is not required for business operations, power it off or remove it from the environment until it can be updated or replaced.

These measures do not eliminate the use-after-free risk but shrink the window an attacker has after obtaining radio privilege.

If your data may have been exposed

Actively exploited vulnerabilities of this type can lead to device compromise and subsequent data exposure. If you suspect devices were targeted before patching, treat them as potentially breached: isolate them, preserve forensic images, and review access logs for lateral movement or data exfiltration. Organizations can also run a free exposure scan of corporate email addresses against known breach data sets to determine whether credentials or other information associated with the environment have already appeared in public dumps. Continue monitoring for unusual activity even after remediation is complete.