CVE-2019-1367: Microsoft Internet Explorer Scripting Engine Memory Corruption Vulnerability

CVE-2019-1367 is a memory corruption vulnerability in the scripting engine of Microsoft Internet Explorer. An attacker who successfully exploits it can run code in the security context of the logged-on user. Because the flaw has been tied to ransomware activity, organizations still running Internet Explorer should treat it as a high-priority risk and confirm their exposure against the vendor advisory.

Successful exploitation requires the victim to process malicious content that reaches the scripting engine, typically through browsing or embedded web content. The result is remote code execution under the current user’s privileges, which can lead to further compromise of the endpoint and lateral movement.

How it works

The vulnerability is classified as CWE-787 (out-of-bounds write). The Internet Explorer scripting engine mishandles objects in memory, allowing memory corruption. An attacker can craft content that triggers the flawed handling path; once memory is corrupted, the attacker can redirect execution flow to achieve code execution in the context of the current user.

No special privileges beyond the ability to deliver content to the browser are required for the initial trigger. Specific exploit mechanics, exact trigger conditions, and any version-specific details must be confirmed against the Microsoft advisory; public technical write-ups should be treated as secondary sources only.

Am I affected? How to find it in your systems

Internet Explorer historically shipped with Windows client and server editions and may still be present even when Microsoft Edge is the default browser. Inventory every Windows system for the presence of iexplore.exe and the associated scripting-engine components (jscript.dll and related libraries).

• Use software inventory or endpoint-management tools to enumerate installed Internet Explorer versions and the last-applied cumulative update.
• Check Group Policy and configuration baselines for any remaining IE-based application compatibility modes, enterprise-mode site lists, or ActiveX controls that force IE rendering.
• Review web-proxy, DNS, and endpoint logs for unusual process creations spawned by iexplore.exe, unexpected network connections originating from the browser process, or crashes of the scripting engine that coincide with browsing activity.
• Confirm the exact affected builds and fixed updates directly from the Microsoft security advisory for CVE-2019-1367; do not rely on version numbers obtained from secondary sources.

How to remediate

Apply the security updates published by Microsoft for this vulnerability, following the vendor’s installation and reboot guidance. After patching, verify that the update is present via the system’s update history or by querying the relevant file versions.

• Remove or disable Internet Explorer where business requirements no longer need it; prefer modern browsers that are actively maintained.
• Enforce least-privilege browsing: ensure users do not run as local administrators, and consider application control or browser sandboxing policies.
• Keep the broader Windows platform current so that related components receive ongoing security fixes.

If you can't patch immediately

Until the vendor update can be deployed, reduce the attack surface and increase detection coverage.

• Segment systems that still require Internet Explorer from high-value networks and restrict outbound web access to only necessary destinations.
• Deploy network or host-based controls (for example, WAF or browser isolation) that can block or sandbox untrusted web content before it reaches the scripting engine.
• Disable or tightly restrict the use of Internet Explorer via software restriction policies, AppLocker, or Windows Defender Application Control where feasible.
• Heighten monitoring for iexplore.exe child processes, unusual module loads, and post-exploitation behaviors commonly associated with ransomware staging.
• Ensure offline backups are current and tested, given the documented ransomware association.

If your data may have been exposed

Actively exploited vulnerabilities of this class have been used to deliver ransomware and other payloads that can lead to data theft or encryption. If you suspect compromise, isolate affected hosts, preserve forensic evidence, and follow your incident-response plan. As an additional check, you can run a free exposure scan of your email addresses against known breach data sets to determine whether credentials or personal information have already appeared in public breach corpora.