CISA's required action for CVE-2013-3893 is to apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. In practice, find every instance of Microsoft Internet Explorer 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 patching CVE-2013-3893 should look like in practice
Start by locating every Internet Explorer deployment, including older Windows images, VDI pools, kiosks, and any system that still launches IE through compatibility or legacy application paths. Treat the vendor security update as the preferred fix, then verify that the system is no longer exposed on the internet if you cannot fully remediate. Use the vendor advisory and the CISA KEV catalog for version-specific guidance.
When you are running a broader patch program, handle this like a confirmed exploited vulnerability rather than a routine update. The most important operational question is not whether the browser is still user-facing, but whether it can still execute in a reachable context. NHIMG’s Vulnerability Management Guide is useful here because it frames scope, prioritisation, verification, and exception handling as one workflow rather than separate tasks.
If IE is still present for a business reason, reduce the reachable attack surface first: remove internet access where possible, confine the browser to a controlled segment, and ensure users cannot casually invoke it for general web access. In environments where browser hardening matters more broadly, Enterprise Browser and Browser Security Guide is a practical companion for thinking about isolation, policy enforcement, and limiting browser-mediated exposure.
When mitigation has to substitute for patching
If a vendor fix cannot be applied immediately, do not leave the decision as “accept the risk and revisit later.” The workable mitigation is to remove the product from any internet-facing role, block unnecessary launch paths, and narrow who can execute or interact with the browser on that host. That is a containment decision, not a permanent solution, and it should have an owner and an expiry date.
For legacy software, the highest-value mitigation is usually exposure reduction rather than cosmetic hardening. This is especially true when the weakness is in a widely reachable client component, because the control failure is often access to the vulnerable code path itself. The patching playbook in Patch Management Guide and the procurement perspective in Patch Management Buyer's Guide both help teams decide how to handle emergency patching, rollback, and exceptions without losing operational control.
If the product cannot be safely isolated or updated, discontinuation is the right answer. That means planning its removal from workflows, replacing any legacy dependency that still requires it, and documenting the end-state so the host does not quietly drift back into use after the incident passes.
How to check for prior compromise before you close the case
Because CISA placed this vulnerability in KEV, the patching work should be paired with compromise review, not just remediation. Review browser logs, endpoint telemetry, proxy activity, and relevant security tooling for signs that the vulnerable browser was exercised from an untrusted source or used in a suspicious chain leading to download, script execution, or credential theft.
The key judgment is whether the vulnerable software was merely present or actually used during the exposure window. If you find unusual child processes, repeated crash patterns, odd outbound connections, or user reports tied to a suspect webpage, treat that as an incident lead. The CISA Known Exploited Vulnerabilities Catalog is the authoritative reminder that this class of issue deserves active verification, not passive patching.
Where a browser flaw could have exposed saved sessions or related credentials, include credential and session review in the closure criteria. In practice, that means checking whether any accounts used from the affected host should have passwords reset, sessions invalidated, or tokens reviewed, especially if the machine handled privileged work or access to sensitive internal systems.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
NIST CSF 2.0, NIST SP 800-53 Rev 5 and CIS Controls v8 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST CSF 2.0 | GV.RM-01 — Risk Management Strategy | CVE response requires prioritised risk treatment and exception handling. |
| Recommendation — Treat KEV-listed browser exposure as a managed risk decision and document the mitigation or removal path. | ||
| NIST SP 800-53 Rev 5 | SI-2 — Flaw Remediation | The question is about patching or mitigating a software vulnerability. |
| RA-5 — Vulnerability Monitoring and Scanning | Confirming exposure and checking for prior compromise depends on discovery and validation. | |
| IR-4 — Incident Handling | KEV status means compromise review may be needed after exposure to active exploitation. | |
| Recommendation — Apply the vendor fix or approved mitigation and verify the vulnerable software is no longer exposed. Scan for every Internet Explorer instance and validate that remediation removed the vulnerable condition. Investigate suspicious browser activity and escalate if evidence suggests the flaw was exploited. | ||
| CIS Controls v8 | CIS-7 — Continuous Vulnerability Management | This is a vulnerability remediation and prioritisation problem. |
| CIS-4 — Secure Configuration of Enterprise Assets and Software | Mitigation may require reducing exposure and hardening legacy software use. | |
| Recommendation — Prioritise, remediate, and verify the browser vulnerability using a tracked vulnerability workflow. Harden or isolate legacy browser hosts so the vulnerable component is not internet reachable. | ||
Practitioner Guidance
What to prioritise: Inventory first, because you cannot mitigate what you cannot locate. For legacy browsers, the practical priority order is exposure removal, patch application, and then validation that the vulnerable code path is no longer reachable.
What to verify: Confirm that the update or mitigation actually changed the reachable state of the host. A system that still has IE installed but is supposedly “not used” is not closed until policy, access, and network controls make that claim true.
Escalation / exception: If a business owner insists on keeping IE available, require an explicit exception with a removal date, compensating controls, and a review trigger tied to the next vulnerability advisory or business change.
Practitioner takeaway: For a KEV-listed browser flaw, success is measured by eliminated exposure and validated containment, not by whether a patch was merely deployed somewhere in the estate.
Related resources from NHI Mgmt Group
- CVE-2013-3893 (Microsoft Internet Explorer Resource Management Errors)
- How do you patch or mitigate CVE-2010-0249 (Microsoft Internet Explorer Use-After-Free)?
- How do you patch or mitigate CVE-2010-0806 (Microsoft Internet Explorer Use-After-Free)?
- How do you patch or mitigate CVE-2022-44698 (Microsoft Defender SmartScreen Security Feature Bypass)?
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Reviewed and updated by the NHIMG editorial team on October 19, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org