CVE-2024-30040: Windows MSHTML platform security feature bypass via improper input validation

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 17 September 2026. Confidence: medium.

high priorityIt is confirmed exploited in the wild and listed in CISA KEV with a near-term remediation deadline, though it requires user interaction and has a moderate EPSS score.

What it is

CVE-2024-30040 is a security feature bypass in the Windows MSHTML platform caused by improper input validation. Because MSHTML is the legacy rendering engine still reachable through Office and other Windows components, bypassing its protections can let an attacker evade the safeguards that normally block malicious content from executing. Microsoft rates it 8.8 (HIGH) with a network vector and required user interaction.

Impact

An attacker can bypass MSHTML security features and, in the CVSS assessment, achieve high confidentiality, integrity and availability impact on the target system. In practice this typically means code execution or script execution in the context of the victim, depending on how the bypass is chained.

Attack surface

Reached over the network (AV:N) with no privileges required (PR:N), but exploitation requires user interaction (UI:R), such as opening a crafted document or visiting a malicious page that loads MSHTML content. No authentication is needed on the attacker's side.

Exploitation

CVE-2024-30040 is listed in CISA's Known Exploited Vulnerabilities catalog (added 2024-05-14, remediation due 2024-06-04), confirming exploitation in the wild. EPSS gives a 30-day probability of about 3.9 percent (89th percentile), and CISA records no known ransomware campaign use.

What to do

• Apply the Microsoft May 2024 security update for the affected Windows versions listed in the MSRC advisory.
• Prioritize patching per the CISA KEV due date of 2024-06-04 for internet-facing and user-workstation systems.
• Reduce exposure to MSHTML-based content where feasible, for example by restricting legacy web rendering in Office and blocking untrusted ActiveX or script content.
• Enforce attachment and web filtering plus macro-blocking policies to cut off the user-interaction path this flaw depends on.
• If patching cannot be completed, follow vendor mitigation guidance or discontinue use of the affected component as CISA directs.

Detection

• Monitor for Office or browser processes spawning child processes such as script hosts or command shells after opening documents or web content.
• Alert on MSHTML-related module loads (for example mshtml.dll) in unusual parent processes or from user-writable directories.
• Review endpoint telemetry for exploitation attempts against MSHTML protections and correlate with email or web delivery events.
• Track patch state across the listed Windows 10, Windows 11 and Windows Server builds and flag unpatched hosts.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.