How do you patch or mitigate CVE-2016-3351 (Microsoft Internet Explorer and Edge Information Disclosure)?

What this CVE means in practice

CVE-2016-3351 is an information disclosure issue in Microsoft Internet Explorer and Edge, so the immediate job is less about “hardening the browser” in the abstract and more about removing a specific exposure path. If the affected browser is still installed, treat it as a live asset, confirm where it is used, and follow the vendor instructions for the security update or mitigation path.

The practical question is whether the browser is still reachable on endpoints that matter. In enterprise estates, older browser components often persist through compatibility settings, legacy shortcuts, or bundled enterprise workflows, which is why exposure review has to be asset-driven rather than assumption-driven. Enterprise Browser and Browser Security Guide is useful here because the same browser control surface often determines whether a mitigation is actually durable.

Patch, mitigation, and decommissioning choices

The first-choice fix is to apply the vendor security update exactly as instructed. If patching is delayed, use the documented mitigation and reduce exposure by removing internet-facing use, restricting access to the affected browser to only what is absolutely necessary, or taking it out of service where business impact allows. The right answer depends on whether the browser is still needed for a workload that cannot yet move.

For browser-class flaws, mitigation quality matters as much as patch status. A browser that remains installed but is no longer allowed to reach untrusted content can be an acceptable temporary control, but it is still a temporary control. If the browser is only required for a specific internal function, isolate that function and stop using the browser for general web access until the update is in place.

Use the vendor advisory and the CISA Known Exploited Vulnerabilities Catalog to confirm the required action and to verify whether the issue is being treated as actively exploited. For vulnerability handling more broadly, Vulnerability Management Guide helps frame the operational side, asset scope, prioritisation, exceptions, and remediation verification.

What to check after remediation

After patching or mitigation, review logs and telemetry for evidence of earlier exploitation. With information disclosure issues, the useful question is not only whether the endpoint was vulnerable, but whether the flaw may have exposed data that could support follow-on access, session abuse, or lateral movement. If the browser handled sensitive authentication material or saved credentials, those should be treated as potentially exposed even when the browser itself now appears fixed.

If investigation shows suspicious activity during the exposure window, rotate any relevant credentials, invalidate sessions, and review adjacent systems the browser could access. That includes shared workstations, admin portals, and any internal applications that trusted the affected endpoint. FIRST is a useful reference point for incident handling discipline when the goal is to determine whether disclosure stayed theoretical or became an intrusion enabler.

Risk and Threat Considerations

Information disclosure in a browser is dangerous because it can turn ordinary user activity into a source of secrets, session material, or internal data that an attacker can reuse. The browser may not be the final target, it may be the bridge to something more valuable, especially if users browse management consoles, internal portals, or authenticated web apps from the same machine.

Failure mechanism: The flaw exposes data that should have remained private, and that leaked data can be combined with phishing, session replay, privilege escalation, or follow-on exploitation against other services the endpoint can reach.

Impact: Even a “disclosure” issue can become an account compromise problem, a data exposure problem, or a foothold for broader intrusion if logs, browser storage, or active sessions were available during the vulnerable period.

Practitioner Guidance

What to prioritise: Identify every endpoint where Internet Explorer or Edge still exists, then separate “installed” from “actually exposed.” The highest-risk cases are browsers that can still reach the internet, handle authenticated sessions, or sit on systems used for administration.

What to verify: Confirm that the vendor update or mitigation was applied to the correct browser build and that any temporary restriction really removed exposure. If you only changed policy but did not reduce reachability, treat the risk as still open.

Decision rule: If patching is possible, patch first. If patching must wait, constrain or remove the browser from service, then re-check for compromise indicators before returning it to normal use.

Practitioner takeaway: For browser disclosure CVEs, remediation is not complete when the patch lands, it is complete when you have eliminated exposure and proven the browser was not used as an information source for later abuse.

Related resources from NHI Mgmt Group

• How do you patch or mitigate CVE-2016-0162 (Microsoft Internet Explorer Information Disclosure)?
• How do you patch or mitigate CVE-2013-7331 (Microsoft Internet Explorer Information Disclosure)?
• Is CVE-2016-3351 (Microsoft Internet Explorer and Edge Information Disclosure) being exploited in the wild?
• How do you patch or mitigate CVE-2017-0059 (Microsoft Internet Explorer Information Disclosure)?