CISA’s required action for CVE-2021-25394 is to apply updates per vendor instructions or discontinue use of the product if updates are unavailable. In practice, find every instance of Samsung Mobile Devices in your estate, apply the vendor security update or documented mitigation, and if no fix can be applied, remove internet exposure or take the product out of service.
What makes CVE-2021-25394 a patching problem rather than just a software update?
This is a race condition in Samsung Mobile Devices, so the practical issue is not only whether an update exists, but whether the vulnerable condition can be reached on devices still in service. A race condition often becomes exploitable when timing, privileges, or reachable interfaces line up, which is why exposure inventory matters as much as the patch itself.
For mobile fleets, the first decision is whether the affected devices are still supported and centrally managed. If a security update is available, treat it as a normal remediation path; if not, the remaining options are containment and retirement. The Mobile Device Security Guide is a useful companion when you need to decide whether MDM, app controls, or enrollment state can reduce the reachable attack surface before removal.
Because the direct answer is vendor-driven, do not try to substitute a generic hardening step for the vendor’s documented fix. If the device is exposed to the internet, externally reachable services, or unmanaged app behavior, the race condition can remain practically relevant even when the device appears low risk. If you need a broader remediation workflow for exposed vulnerabilities, the Vulnerability Management Guide is the best fit for scoping, prioritisation, and verification.
How should you confirm exposure before you decide to patch or retire?
Start with inventory, not assumptions. You need a list of every Samsung Mobile Device variant, ownership state, management state, and deployment location, then a check for whether the vendor update path is actually available in your environment. On mobile estates, the same product can be present as corporate-owned, BYOD-enrolled, or partially managed, and each case changes what you can enforce quickly.
Verification should include whether the device is still receiving vendor updates, whether end users can delay installation, and whether the affected device is reachable from untrusted networks or internet-facing services. The CISA Known Exploited Vulnerabilities Catalog should be checked alongside the vendor advisory so you are working from the authoritative remediation posture, not from secondary summaries.
If you manage many endpoints, the useful question is not only “is it vulnerable?” but “can I reliably force the fix?” That means confirming update policy enforcement, enrolment health, and whether your mobile controls can prove that the remediated build actually landed. Where patch compliance is uncertain, containment may be safer than hoping users self-update.
What to do when patching must wait, or the device cannot be updated
If you cannot immediately apply the vendor update, reduce reachable exposure first. That usually means removing the device from any internet-facing role, limiting app and network reachability, and preventing the vulnerable system from acting as a trusted bridge into internal resources. For a mobile device, that can be more important than waiting for a perfect maintenance window.
Where the product is business-critical and cannot be retired right away, use the smallest effective containment step that actually changes the risk. In practice that can mean restricting connectivity, disabling unnecessary services, and narrowing what the device can reach from corporate networks. The CIS Benchmarks provide a useful hardening mindset, even when the specific control set must be adapted to mobile and managed-device realities.
If no update or mitigation is available from the vendor, discontinuing use is not an overreaction, it is the expected fallback for an unsupported vulnerable product. The key judgement is whether the residual exposure is acceptable for the business function the device still performs. If the answer is no, removal from service is the cleanest mitigation.
Risk and Threat Considerations
Race conditions are risky because they can turn an apparently valid operation into an unsafe one when timing, concurrency, or state changes are manipulated. On mobile devices, that can lead to unexpected behavior, local privilege effects, or a reachable condition that defenders do not notice until after exploitation or instability.
Failure mechanism: An attacker or malformed process may trigger the vulnerable timing window before the device finishes enforcing the intended state, allowing an action that should have been blocked or synchronised to succeed out of order.
Impact: The practical impact can range from service instability to security control bypass on devices that remain exposed, especially when the product stays online without vendor remediation or compensating containment.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
CIS Controls v8, NIST CSF 2.0 and NIST SP 800-53 Rev 5 set the technical controls, while ISO/IEC 27001:2022 defines the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| CIS Controls v8 | CIS-7 — Continuous Vulnerability Management | This CVE requires inventory, prioritization, and verified remediation of vulnerable devices. |
| Recommendation — Track affected devices, prioritize remediation, and verify the vulnerable condition is removed. | ||
| NIST CSF 2.0 | PR.IP-12 — Vulnerability Management | The question is about patching or mitigating a known exploited vulnerability on endpoints. |
| PR.AA-01 — Identities and Credentials Are Managed | Device access and exposure reduction depend on controlling who and what can reach the product. | |
| Recommendation — Apply a vulnerability management process to identify, remediate, and verify affected devices. Restrict access paths to the vulnerable device until remediation is complete. | ||
| ISO/IEC 27001:2022 | A.8.8 — Management of technical vulnerabilities | This is a classic technical vulnerability handling case requiring update or retirement decisions. |
| Recommendation — Maintain a process to apply vendor fixes or remove unsupported vulnerable systems. | ||
| NIST SP 800-53 Rev 5 | RA-5 — Vulnerability Monitoring and Scanning | The response requires finding every instance and confirming exposure before choosing mitigation. |
| Recommendation — Continuously identify vulnerable devices and verify remediation or containment. | ||
Practitioner Guidance
What to prioritise: Patchable devices first, then unsupported or unpatchable devices that still have network exposure. A device that cannot be updated but remains reachable is usually the highest-risk case, even if it is not the most visibly broken one.
What to verify: Confirm that the vendor update was actually applied, not merely queued, and verify that the device cannot still be reached in the same way after remediation. For mobile fleets, install-state proof matters as much as policy intent.
Decision rule: If the device can be updated, update it. If it cannot be updated and the vulnerability remains reachable, remove exposure or retire the device rather than leaving it in a partially mitigated state.
Practitioner takeaway: For KEV-listed mobile flaws, the right question is not whether you have a patch plan, but whether you can prove the vulnerable device is no longer reachable in the way that matters.
Related resources from NHI Mgmt Group
- How do you patch or mitigate CVE-2021-25395 (Samsung Mobile Devices Race Condition)?
- Is CVE-2021-25394 (Samsung Mobile Devices Race Condition) being exploited in the wild?
- How do you patch or mitigate CVE-2021-25487 (Samsung Mobile Devices Out-of-Bounds Read)?
- How do you patch or mitigate CVE-2021-25489 (Samsung Mobile Devices Improper Input Validation)?