CVE-2018-0798 is a memory corruption vulnerability in Microsoft Office. CISA added it to the Known Exploited Vulnerabilities catalogue on 3 November 2021, which means attackers have used it in real attacks. Microsoft Office contains a memory corruption vulnerability due to the way objects are handled in memory. This vulnerability is known to be chained with CVE-2018-0802.
What This Vulnerability Means in Microsoft Office
Memory corruption in an application like Microsoft Office means attacker-controlled content can disturb how the program allocates, references, or frees memory. In practice, that can turn a document or embedded object into a reliable code execution path, which is why these flaws are treated as high-value exploitation targets.
For a publicly tracked issue, the first reference point should always be the authoritative record. Use the CVE Program entry format to anchor the identifier, and use NIST National Vulnerability Database for the canonical CVE record and related metadata.
Why It Is Dangerous When Chained
The added danger here is not just the memory corruption itself, but the way it can be combined with another flaw in a multi-stage exploit chain. The page already notes that this CVE is known to be chained with CVE-2018-0802, and that matters because chained exploits often let attackers move from initial document parsing to deeper compromise with fewer user-visible signs.
That pattern is common in real-world exploitation of office-suite vulnerabilities: one issue creates the entry point, another stabilises or extends execution, and the combined chain increases reliability. The result is often weaponised file delivery, hidden payload execution, or follow-on staging that looks like normal document activity until compromise is already underway.
How Organisations Assess Exposure and Reduce Blast Radius
Exposure assessment starts with asset inventory, product version knowledge, and a clear view of where Microsoft Office is installed and exposed to untrusted content. Teams should confirm which endpoints, virtual desktops, mail gateways, file-sharing paths, and document workflows can receive malicious office files, then compare that estate against vendor guidance and the CVE record.
Remediation should be driven by the vendor advisory and the KEV context rather than guesswork. Where patching cannot happen immediately, limit document origin paths, reduce exposure to high-risk file types, harden attachment handling, and narrow who can open externally sourced content.
For broader patch prioritisation and verification discipline, Vulnerability Management Guide is useful for the surrounding process of scoping, prioritisation, and remediation tracking.
Detection, Investigation, and Identity Impact After Exploitation
Detection is usually strongest when organisations correlate suspicious document open events, abnormal Office child processes, crash patterns, and unusual outbound activity soon after file delivery. If a patch has already been applied, investigators should still review whether the system was compromised before remediation, because successful exploitation may leave persistence or post-exploitation tooling behind.
Where Office exploitation is used as an entry path, the identity impact can be material even if the vulnerability is not itself an identity issue. Users, service accounts, tokens, and connected cloud sessions may need review if the compromised host could have exposed credentials, authentication material, or access to synced content.
The practical lesson from real-world exploitation is that document-based entry points often become credential theft or lateral movement problems shortly after initial execution. For a wider view of how attackers convert initial access into broader compromise, see the State of NHI & AI Agent Breach Report 2026 and Vulnerability Management Guide for the remediation lifecycle that follows detection.
Risk and Threat Considerations
Memory corruption in a widely used office suite is attractive because attackers can deliver it through ordinary document workflows and exploit trust in common file formats. Once weaponised, it can support remote code execution, staged payload delivery, and compromise that is difficult to distinguish from normal user activity at first glance.
Failure mechanism: The exploit chain abuses unsafe object handling in memory, allowing crafted content to disturb program state and trigger attacker-controlled execution when the document is opened or processed.
Impact: Successful exploitation can give attackers code execution on user systems, which may lead to credential theft, malicious document propagation, persistence, and further lateral movement inside the environment.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
MITRE ATT&CK addresses the attack and risk surface, while CIS Controls v8, NIST SP 800-53 Rev 5 and OWASP ASVS set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| CIS Controls v8 | CIS-7 — Continuous Vulnerability Management | This CVE requires ongoing identification and remediation of exposed software flaws. |
| Recommendation — Prioritise and remediate exposed Office instances using continuous vulnerability management. | ||
| NIST SP 800-53 Rev 5 | SI-2 — Flaw Remediation | The issue is a known software flaw that must be tracked and remediated promptly. |
| RA-5 — Vulnerability Monitoring and Scanning | Exposure assessment depends on locating vulnerable Office installations and verifying remediation. | |
| Recommendation — Track the Office flaw and apply remediation through formal flaw management. Scan for vulnerable Office deployments and verify remediation status. | ||
| OWASP ASVS | V15 — Secure Coding and Architecture | Memory corruption is a software integrity failure class relevant to secure design and review. |
| Recommendation — Review code handling patterns that can produce memory corruption in document-processing paths. | ||
| MITRE ATT&CK | T1203 — Exploitation for Client Execution | Office document exploitation is a classic client-side execution path. |
| Recommendation — Map malicious document opens to client-execution detections and response playbooks. | ||
Practitioner Guidance
Why practitioners should care: Treat this as more than a single application defect, because office-suite exploitation often becomes an endpoint and identity compromise problem quickly. The highest-value follow-up work is confirming whether the vulnerable host was isolated from sensitive accounts, sessions, and file shares before the issue was fixed.
What to watch for: Look for suspicious file-open telemetry, unexpected Office spawning of child processes, new persistence on endpoints, and signs that user credentials or authenticated sessions were exposed during the incident window. If exploitation is suspected, review nearby systems that may have ingested the same file or shared the same trust path.