Is CVE-2021-42292 (Microsoft Excel Security Feature Bypass) being exploited in the wild?

Yes. CISA added CVE-2021-42292 to its Known Exploited Vulnerabilities catalogue on 17 November 2021, which it does only when there is reliable evidence of active exploitation. CISA has not linked it to known ransomware campaigns. A security feature bypass vulnerability in Microsoft Excel would allow a local user to perform arbitrary code execution. Any organisation running the affected product should treat remediation as urgent.

What “being exploited in the wild” means for this CVE

For a vulnerability question like this, the key signal is not theoretical exploitability, but whether credible exploitation has already been observed often enough to trigger inclusion in CISA’s KEV catalogue. That moves the issue from “patch when convenient” to active exposure management, because the product is already a live target and the window for safe delay is shorter.

When a flaw sits in a widely used office application, the practical question is usually how the exploit is delivered, whether user interaction is required, and what execution or access outcome the attacker can obtain. For exploit-in-the-wild judgments, treat the vulnerable application as part of a broader attack chain, not as an isolated bug.

Why this matters operationally for Excel deployments

A security feature bypass in spreadsheet software can matter well beyond the application boundary because documents are a common entry point for phishing, attachment delivery and downstream code execution. If the affected product is present on endpoints that open untrusted files, the real risk is not just a local application issue, but a route into the workstation and then potentially into broader enterprise access.

For Microsoft ecosystems, the answer to “am I exposed?” depends on where Excel is installed, who opens external content, and what local trust assumptions the environment makes. A vulnerability that enables arbitrary code execution after bypassing a security feature is especially important where users routinely open files from email, collaboration tools or shared storage.

Zero-Day and Exploited Vulnerabilities Guide is the right internal reference when you need to triage active exploitation signals, decide how urgently to patch, and plan post-patch hunting after remediation.

Vulnerability Management Guide helps turn KEV status into an operational response, including prioritisation, exception handling and verification after repair.

What to do when patching cannot happen immediately

When remediation is delayed, the priority is blast-radius reduction, not comfort measures. Restrict exposure to the vulnerable software version, limit untrusted document handling, and reduce the number of users and systems that can open externally supplied Excel files while the issue remains unresolved.

That response should also include looking for signs of prior compromise, because KEV status means the issue has already moved beyond proof-of-concept territory. If the environment allowed suspicious spreadsheet content to reach users before remediation, review endpoint telemetry, email attachment history and suspicious child processes spawned by office applications.

CISA Known Exploited Vulnerabilities Catalog is the authoritative place to confirm the current remediation expectation for the issue and to track whether it remains under active exploitation.

NIST National Vulnerability Database remains useful for cross-checking the record, understanding the published vulnerability metadata and linking the CVE to other tracking workflows.

Risk and Threat Considerations

Because this CVE is already in KEV, the main risk is not abstract exposure but ongoing attacker interest. Spreadsheet exploits are valuable to attackers because they can be delivered through routine business workflows and may blend into normal document handling.

Failure mechanism: A security feature bypass can disable a protection that users and defenders expect to stand between a malicious document and code execution, making the trust boundary around file content weaker than it appears.

Impact: If a user opens a weaponized Excel file, the attacker may gain code execution on the local system, which can lead to credential theft, persistence, lateral movement or follow-on compromise depending on endpoint controls and user privilege.

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, OWASP ASVS and NIST CSF 2.0 set the governance and control requirements practitioners need to meet.

Framework	Control / Reference	Relevance
CIS Controls v8	CIS-7 — Continuous Vulnerability Management	KEV-listed CVEs need prioritized remediation and verification.
Recommendation — Prioritize and track remediation for KEV-listed vulnerabilities across exposed systems.
NIST SP 800-53 Rev 5	SI-2 — Flaw Remediation	Active exploitation makes timely flaw remediation the core control response.
Recommendation — Remediate the Excel flaw promptly and confirm deployed systems are patched.
OWASP ASVS	V16 — Security Logging and Error Handling	Post-exploitation checks depend on logs and telemetry from suspicious document activity.
Recommendation — Preserve and review logs that can show malicious document execution or abuse.
NIST CSF 2.0	RS.MA-1 — Incident Management Processes	Exploit-in-the-wild status requires a response process that includes hunting for compromise.
Recommendation — Activate incident response workflows to assess and contain possible exploitation.
MITRE ATT&CK	T1204 — User Execution	Malicious Excel delivery commonly depends on a user opening a crafted file.
Recommendation — Map suspicious spreadsheet delivery to user-execution detection and response.

Practitioner Guidance

What to prioritise: Treat the KEV listing as a high-priority remediation trigger, then confirm where Excel is installed on internet-connected or email-facing endpoints. The most useful first step is to identify users and systems that regularly process external spreadsheets.

What to verify: Validate whether any suspicious Excel-related activity occurred before remediation, especially unusual child processes, unexpected downloads, or document opens from untrusted sources. If you rely on endpoint detection, confirm it can observe office-to-process launch chains.

Decision rule: If you cannot patch immediately, reduce exposure by limiting untrusted document execution paths, increasing user caution around external files, and reviewing for compromise before assuming the environment is clean.

Practitioner takeaway: KEV inclusion means this is an active-exploitation problem, so the right response is rapid remediation plus a compromise check, not just routine patch scheduling.