Is CVE-2021-25395 (Samsung Mobile Devices Race Condition) being exploited in the wild?

What the KEV listing means for this Samsung mobile device issue

CISA’s KEV catalogue is the key signal here because it separates a theoretical vulnerability from one with evidence of active exploitation. For practitioners, that changes priority immediately: the question is not whether the flaw can be weaponised in principle, but whether exposed Samsung fleets are still reachable and whether compensating controls are strong enough to reduce the attack window.

For this class of issue, the practical first step is to confirm which device models, Android build levels, and managed or unmanaged user populations are in scope. Mobile device security guidance such as Mobile Device Security Guide is most useful when it is tied to an actual asset inventory, because an exploited mobile flaw only matters where the affected devices remain deployed and exposed to the relevant trigger conditions.

When a vulnerability has been placed in KEV, the response posture should shift from normal backlog handling to urgent exposure reduction. CISA’s own catalogue and vulnerability workflow should be treated as the authoritative starting point for remediation timing and verification, alongside the vendor advisory for exact device and firmware applicability.

Why a race condition can become a write primitive on mobile hardware

A race condition in a low-level driver is dangerous because it can turn timing into control. In this case, the issue is not a cosmetic crash risk, it is a memory-safety problem that can become a use-after-free and then a write primitive if the vulnerable code path is reached under the right privileges and state transitions. That makes the flaw materially more serious than a generic logic bug.

Race-condition weaknesses are often hard to reason about from a single code path because exploitability depends on concurrency, scheduling, and device-specific behaviour. The broader weakness pattern is captured well in the CWE Top 25 Guide, which helps practitioners think about root cause rather than only the individual CVE label.

On mobile devices, low-level driver issues also sit close to privilege boundaries. If an attacker can combine timing manipulation with a compromised radio privilege or adjacent access path, a driver flaw may become a stepping stone to higher-impact code execution, persistence, or data access on the device itself.

How to prioritise exposure checks, mitigation, and compromise review

The response sequence should be: identify exposed Samsung devices, verify whether they remain in a vulnerable configuration, and apply the vendor fix or approved mitigation as soon as operationally possible. If patching must wait, reduce exposure by tightening device management posture, limiting risky connectivity, and watching for abnormal behaviour around the vulnerable component.

The most relevant remediation discipline is the one used for active exploitation, not ordinary patch hygiene. The Zero-Day and Exploited Vulnerabilities Guide is useful because it frames KEV entries as emergency items that need triage, containment, and post-remediation validation rather than simple scheduling.

If exposure exists, check for earlier compromise even when the device now appears healthy. That means looking for unusual privilege changes, unexpected app behaviour, suspicious radio or device-management activity, and any signs that the vulnerable device has been used as an entry point into accounts, data, or connected services. Where the device stores sensitive credentials or tokens, consider whether session or credential rotation is warranted after confirmed compromise.

Risk and Threat Considerations

An actively exploited mobile driver flaw creates more than a device-local security problem. It can expose user data, weaken trust in mobile endpoints, and provide an attacker with a foothold on a managed or personally owned device that is used to access enterprise services. In a fleet setting, that turns one weakness into a concentration risk if many devices share the same model and configuration.

Failure mechanism: Attackers exploit the race condition to reach a use-after-free state and influence memory writes, which can be chained into privilege abuse or broader device compromise when the vulnerable path is reachable.

Impact: Successful exploitation can lead to unauthorized code execution, device control, or downstream access to enterprise applications and sensitive data that the mobile device can reach.

Practitioner Guidance

What to verify: Confirm device model, firmware level, management state, and whether any compensating control actually reduces exposure on the affected population. Do not assume “mobile MDM present” equals “risk removed” unless the vulnerable path is truly blocked or remediated.

Decision rule: If the device is in scope and still exposed, treat it as a priority remediation item, even if you have not seen obvious abuse. If the device cannot be patched immediately, isolate or restrict it until remediation is complete.

What practitioners underestimate: Mobile exploitation is often judged by user-visible symptoms, but active abuse may leave little obvious evidence. The safer assumption for a KEV-listed mobile flaw is that exposure itself is the risk signal, and the investigation should be driven by reachability and trust impact, not by visible instability alone.

Practitioner takeaway: For a KEV-listed mobile vulnerability, the key question is not whether exploitation is imaginable, it is whether the affected device class is still reachable in your environment and whether you can reduce the blast radius before the fix is fully everywhere.

Related resources from NHI Mgmt Group

• Is CVE-2021-25394 (Samsung Mobile Devices Race Condition) being exploited in the wild?
• How do you patch or mitigate CVE-2021-25395 (Samsung Mobile Devices Race Condition)?
• CVE-2021-25395 (Samsung Mobile Devices Race Condition)
• Is CVE-2021-25337 (Samsung Mobile Devices Improper Access Control) being exploited in the wild?