How do you patch or mitigate CVE-2016-3298 (Microsoft Internet Explorer Messaging API Information Disclosure)?

CISA’s required action for CVE-2016-3298 is to apply updates per vendor instructions. 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. After patching, review logs for signs of earlier exploitation, because attackers used this flaw in the wild.

What CVE-2016-3298 means for patching and mitigation

The practical question is not just whether Internet Explorer is installed, but whether it is still reachable on any system where the vulnerable Messaging API could be invoked. Treat this as a normal vulnerability-remediation task: confirm exposure, apply the vendor update, and where patching is blocked, reduce exposure by removing internet access or taking the product out of service.

For a browser flaw like this, the most important operational issue is estate visibility. Use your asset inventory, browser management tooling, and vulnerability scan results to find every surviving Internet Explorer instance, including legacy VDI, kiosk, and long-tail endpoints that often evade standard cleanup cycles.

When you review the vendor fix path, anchor the work to the browser control plane rather than one-off endpoint handling. An Enterprise Browser and Browser Security Guide is a useful reminder that browser exposure is often a configuration and lifecycle problem, not just a patching problem.

How to confirm exposure and apply the vendor fix

Start by identifying where Internet Explorer still exists, then determine whether the affected code path is reachable in your operating environment. If a supported update is available, apply it using the vendor’s documented method and verify that the update was installed successfully on every in-scope system.

If you manage endpoints centrally, prioritize the systems that are internet-facing, used for administrative access, or embedded in business processes that cannot tolerate browser removal without a fallback. The safest order is the systems with the broadest reach first, then the hardest-to-find legacy hosts.

For broader remediation discipline, use the same lifecycle thinking you would use for any exploited weakness. A Vulnerability Management Guide fits this work because the issue is about finding affected assets, applying the vendor action, and confirming closure rather than assuming a single patch event solved the problem.

What to do if patching has to wait

If you cannot apply the fix immediately, the mitigation goal is to remove the attack surface the flaw depends on. In practice that means blocking internet access to the vulnerable browser, disabling use where possible, or retiring the product from service on systems that do not absolutely require it.

Temporary compensating controls should be treated as short-lived. Keeping an exploitable browser accessible because a business process is inconvenient is usually a risk acceptance decision, not a mitigation. Document the exception, set an expiry, and make ownership explicit so the exposure does not become permanent by default.

If the browser is being used in a way that also exposes session material, saved credentials, or other sensitive browsing data, tighten browser policy at the same time. The broader control lesson from browser security guidance is that reducing reach and reducing stored sensitive state often matter as much as patching itself.

Risk and Threat Considerations

This CVE matters because it was exploited in the wild, which means delayed remediation can move the issue from theoretical exposure to actual compromise. The main risk is not only information disclosure, but what attackers can do after learning more about the environment or user state through the vulnerable browser path.

Failure mechanism: A vulnerable Internet Explorer installation remains reachable, the flaw is triggered before remediation, and the attacker gains information that can support follow-on abuse, persistence, or further targeting.

Impact: Exposed systems may reveal enough detail to help an attacker refine exploitation or prioritize later intrusion steps, so unpatched browsers should be treated as active risk until the vendor action is complete and exposure is reduced.

Standards & Framework Alignment

This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.

CIS Controls v8 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 identifying, prioritizing, and remediating exposed software.
Recommendation — Scan for affected systems and drive remediation to closure with tracked exceptions.
NIST SP 800-53 Rev 5	RA-5 — Vulnerability Monitoring and Scanning	The answer depends on finding every vulnerable Internet Explorer instance.
	SI-2 — Flaw Remediation	CISA directs applying vendor updates or mitigation for the flaw.
	AU-6 — Audit Record Review, Analysis, and Reporting	Post-patch log review is needed to detect earlier exploitation.
Recommendation — Continuously scan for the vulnerable browser and verify remediation results. Apply the vendor update or approved mitigation and confirm deployment. Review logs after remediation for evidence of prior exploitation.
ISO/IEC 27001:2022	A.8.8 — Management of technical vulnerabilities	The subject is the lifecycle handling of a known exploitable vulnerability.
Recommendation — Track, remediate, and document the vulnerability until exposure is closed.

Practitioner Guidance

What to verify: Confirm not only that the update was deployed, but that no legacy Internet Explorer instance remains reachable from a user workstation, management host, or externally accessible segment. A patch that exists somewhere in the estate is not the same thing as a closed exposure.

What to measure: Track the count of remaining Internet Explorer installations, the number of exceptions still in force, and the time from exposure discovery to remediation or removal. Those three signals tell you whether the issue is being eliminated or merely deferred.

Practitioner takeaway: For exploited browser CVEs, remediation is complete only when the vulnerable software is updated or removed and the exposure path is no longer usable, with logging reviewed for signs that the flaw was already abused.