Microsoft Outlook MonikerLink Remote Code Execution
A vulnerability in how Microsoft Outlook processes specially crafted hyperlinks (the "MonikerLink" flaw) allows an attacker to bypass Outlook's Protected View and trigger remote code execution simply by having a user click a malicious link in an email.
- Vendor
- Microsoft
- Product
- Outlook (Microsoft 365 Apps, Office 2016–2021)
- CVSS
- 9.8
- EPSS (exploit probability)
- 94.7%
- Status
- kev
- CISA patch-by (BOD 22-01)
- Published
Is CVE-2024-21413 being exploited?
Yes. CISA added CVE-2024-21413 to its Known Exploited Vulnerabilities catalog on . CISA only lists a CVE when it has reliable evidence of exploitation in the wild.
FIRST's EPSS model puts the probability of exploitation activity in the next 30 days at 94.7% (scored October 14, 2026).
- CISA KEV[ LISTED ]
- ENISA EUVD (exploited)[ — ]
- CIRCL KEV[ — ]
Catalog snapshot 2026-11-13. Full cross-catalog view: /kev-comparison
CVE-2024-21413 timeline
Every event links to its source. Catalog dates are each catalog's own; day offsets count from NVD publication. Data: JSON
What to do
US federal civilian agencies must remediate by (21 days after listing) under BOD 22-01. Everyone else: that deadline is a sensible upper bound, not a target. Vendor guidance and the NVD record are linked under Source above.
CVE-2024-21413, nicknamed “MonikerLink” by the researcher who reported it (Check Point Research), is a remote-code-execution vulnerability in Microsoft Outlook. By crafting a hyperlink using the file:// moniker syntax with a specific exclamation-mark suffix, an attacker could cause Outlook to bypass Protected View entirely — the sandboxing feature meant to neutralize risky content from untrusted documents — and open the file directly, leading to code execution and, in some configurations, NTLM credential leakage.
Microsoft patched the vulnerability as part of its February 2024 Patch Tuesday release. Unlike several other entries in this tracker, MonikerLink had not been confirmed as exploited in the wild at time of disclosure, but its low complexity (no special privileges, minimal user interaction beyond a single click) and the ubiquity of Outlook made it a high-priority patch for enterprises.
Why it mattered
Outlook is one of the most widely deployed email clients in the world, and a flaw that defeats Protected View with one click is exactly the kind of bug ransomware affiliates look for as an initial-access vector. Security teams treated this as a “patch immediately” item even absent confirmed in-the-wild exploitation, given how often Protected View bypasses get weaponized shortly after disclosure.
See Microsoft’s own MSRC advisory and the NVD record above for affected version ranges and patch guidance.
Other Microsoft CVEs we track
| CVE / Vulnerability | Severity | CVSS | EPSS | Added to KEV |
|---|---|---|---|---|
| CVE-2026-124194 Microsoft Office Outlook Missing User Interaction for Potentially Unsafe Action Vulnerability | [ MEDIUM ] | 6.5 | 1.6% | |
| CVE-2026-96951 Microsoft Windows Command Injection Vulnerability | [ HIGH ] | 8.8 | 9.8% | |
| CVE-2026-96940 Microsoft Exchange Server privilege escalation via weak authorizationwrite-up | [ HIGH ] | 8.8 | 2.7% | — |
| CVE-2026-65660 Microsoft SharePoint Code Injection Vulnerabilitywrite-up | [ HIGH ] | 8.8 | 9.9% | |
| CVE-2026-85889 Azure AI Foundry missing authentication allows unauthorized privilege escalationwrite-up | [ CRITICAL ] | 10.0 | 0.7% | — |
| CVE-2026-69843 Microsoft Fabric authentication bypass by spoofingwrite-up | [ CRITICAL ] | 10.0 | 0.9% | — |
| CVE-2026-85880 Microsoft Windows ALPC Heap Buffer Overflow Privilege Escalationwrite-up | [ HIGH ] | 7.8 | 0.4% | |
| CVE-2026-81963 Microsoft Windows Update Stack Link-Following Privilege Escalationwrite-up | [ HIGH ] | 7.8 | 7.1% |
