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Actively exploited

CVE-2016-3298 Microsoft Internet Explorer Messaging API Information Disclosure Vulnerability

An information disclosure vulnerability exists when the Microsoft Internet Messaging API improperly handles objects in memory. An attacker who successfully exploited this vulnerability could allow the attacker to test for the presence of files on disk.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch urgentlyCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 24 May 2022.
  • Rated Medium severity (CVSS 6.5, scored by CISA).
  • It has been in the catalogue for 1,627 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

Microsoft Internet Explorer 9 through 11 and the Internet Messaging API in Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, and Windows 7 SP1 allow remote attackers to determine the existence of arbitrary files via a crafted web site, aka "Internet Explorer Information Disclosure Vulnerability."

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Microsoft Internet Explorer. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply updates per vendor instructions.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsCyber Essentials requires high and critical updates (CVSS 7.0 or above) within 14 days of release. Treat any exploited flaw the same way.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 14 Jun 2022 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2016-3298
  3. CVE record: CVE-2016-3298
  4. FIRST EPSS
  5. docs.microsoft.com/en-us/security-updates/securitybulletins/2016/ms16-118
  6. docs.microsoft.com/en-us/security-updates/securitybulletins/2016/ms16-126
  7. securityfocus.com/bid/93392
  8. securitytracker.com/id/1036992