CVE-2018-0824

What is COM in Windows?

Component Object Model (COM) is the foundational inter-process communication and object-instantiation framework underlying much of Windows and Office application functionality, allowing one process to create and call methods on objects hosted by another. Because COM objects can be serialized and passed between processes, and in some configurations between machines over RPC, flaws in how that serialized data is reconstructed sit at a particularly sensitive layer of the operating system.

Overview

CVE-2018-0824 is a high-severity remote code execution vulnerability in Microsoft COM for Windows, caused by insecure deserialization of untrusted data. An attacker who can deliver a specially crafted file or script to a target, for example via email or a malicious webpage, can trigger the vulnerable deserialization path, potentially leading to arbitrary code execution or privilege escalation in the context of the user who processed the malicious data. Exploitation requires user interaction, such as opening a file, consistent with its Required user-interaction CVSS metric.

Technical Details

The vulnerability is classified under CWE-502 (deserialization of untrusted data): when a COM-based component reconstructs a serialized object from attacker-controlled input, it does not adequately validate the resulting object's type or contents before invoking further functionality, allowing a maliciously crafted object graph to trigger unintended code paths - a pattern conceptually similar to Java deserialization gadget-chain attacks, applied here to Windows' native COM/RPC data-marshaling layer. The Network attack vector combined with required user interaction points to a file- or script-based delivery mechanism reaching a target machine and being processed locally.

Discovery

This vulnerability was patched by Microsoft as part of its May 2018 Patch Tuesday release, addressed through Microsoft's standard internal security response process.

Exploitation Context

CISA added this vulnerability to the KEV catalog in August 2024, more than six years after the original patch, which strongly indicates it was identified as being used in active attacks well after initial disclosure - a pattern seen with several older Windows CVEs that quietly become useful again once patch compliance for aging, low-visibility fixes lapses across large fleets of legacy systems. This long gap between patch and confirmed exploitation underscores why aging, easy-to-overlook CVEs still warrant remediation.

Remediation

1. Confirm all Windows systems have applied the May 2018 (or later cumulative) security update addressing this vulnerability.
2. Prioritize patching on any systems that may have been running unpatched or unsupported Windows versions for extended periods, since this CVE's late KEV addition suggests continued exposure in such environments.
3. Restrict execution of untrusted files and scripts through application allowlisting and attachment filtering.
4. Keep endpoint detection and response tooling updated to catch exploitation attempts targeting legacy deserialization flaws.
5. Review patch management processes to ensure older, already-fixed CVEs are not silently reintroduced through unpatched legacy images or golden AMIs.