{"id":"CVE-2024-21413","published":"2024-02-13T18:16:00Z","modified":"2026-08-10T16:18:51Z","title":"Microsoft Outlook Improper Input Validation Vulnerability","vendor":"Microsoft","product":"Office Outlook","tier":"core","eol":null,"description":{"text":"Microsoft Outlook Remote Code Execution Vulnerability","provenance":"source","from":"NVD"},"summary":{"text":"A flaw in Microsoft Office Outlook stems from improper input validation, which allows remote code execution. An unauthenticated attacker with network access can exploit it without any user interaction and under the default configuration, potentially gaining full control over the affected system.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:09:07Z"},"cvss":{"score":9.8,"severity":"CRITICAL","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.9466,"percentile":0.99856,"date":"2026-10-30","provenance":"source"},"kev":{"dateAdded":"2025-02-06","dueDate":"2025-02-27","ransomware":false,"requiredAction":"Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.","notes":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2024-21413 ; https://nvd.nist.gov/vuln/detail/CVE-2024-21413","provenance":"source"},"vulncheckKev":{"dateAdded":"2024-05-14","exploitedFirstSeen":"2024-05-14","ransomware":false,"evidence":[{"url":"https://web-assets.esetstatic.com/wls/en/papers/threat-reports/eset-apt-activity-report-q4-2023-q1-2024.pdf","date":"2024-05-14"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2025-02-06"},{"url":"https://www.microsoft.com/en-us/security/blog/2025/04/09/stopping-attacks-against-on-premises-exchange-server-and-sharepoint-server-with-amsi/","date":"2025-04-09"},{"url":"https://cyble.com/resources/research-reports/global-cybersecurity-report/","date":"2025-12-11"},{"url":"https://www.loginsoft.com/reports/annually/vulnerability-intelligence-report-2025","date":"2026-01-20"}],"evidenceTotal":5,"provenance":"source"},"exploited":true,"otx":{"pulseCount":50,"pulses":[{"name":"Actively_Exploited_Kev | Oct 30, 2026","url":"https://otx.alienvault.com/pulse/6ae35d889ea92b4ce19c2680","created":"2026-10-29"},{"name":"Actively_Exploited_Kev | Oct 29, 2026","url":"https://otx.alienvault.com/pulse/6ae20c1db17e7057ae7d9ad1","created":"2026-10-28"},{"name":"Actively_Exploited_Kev | Oct 28, 2026","url":"https://otx.alienvault.com/pulse/6ae0ba7e0e2a97ff7b218819","created":"2026-10-27"},{"name":"Actively_Exploited_Kev | Oct 27, 2026","url":"https://otx.alienvault.com/pulse/6adf68b85c3e852f3c111d18","created":"2026-10-26"},{"name":"Actively_Exploited_Kev | Oct 24, 2026","url":"https://otx.alienvault.com/pulse/6adb740e397c3ad4799aa4cd","created":"2026-10-23"},{"name":"Actively_Exploited_Kev | Oct 23, 2026","url":"https://otx.alienvault.com/pulse/6ada236fcfba2dfa730ea482","created":"2026-10-22"},{"name":"Actively_Exploited_Kev | Oct 22, 2026","url":"https://otx.alienvault.com/pulse/6ad8d33a077cbb5cab524d80","created":"2026-10-21"},{"name":"Actively_Exploited_Kev | Oct 21, 2026","url":"https://otx.alienvault.com/pulse/6ad78130c4d1ac2be83a8b6d","created":"2026-10-20"},{"name":"Actively_Exploited_Kev | Oct 20, 2026","url":"https://otx.alienvault.com/pulse/6ad62f63c24a405a3423cc13","created":"2026-10-19"},{"name":"Actively_Exploited_Kev | Oct 19, 2026","url":"https://otx.alienvault.com/pulse/6ad4dda174e5797d0bd238b7","created":"2026-10-18"}],"provenance":"machine"},"cwes":[{"id":"CWE-20","name":"Improper Input Validation"}],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2024-21413","tags":["Patch","Vendor Advisory"]},{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2024-21413","tags":["Patch","Vendor Advisory"]},{"url":"https://research.checkpoint.com/2024/the-risks-of-the-monikerlink-bug-in-microsoft-outlook-and-the-big-picture/","tags":["Technical Description"]},{"url":"https://www.vicarius.io/vsociety/posts/cve-2024-21413-critical-monikerlink-vulnerability-affecting-microsoft-outlook-detection-script","tags":["Exploit"]},{"url":"https://www.vicarius.io/vsociety/posts/cve-2024-21413-critical-monikerlink-vulnerability-affecting-microsoft-outlook-mitigation-script","tags":["Mitigation"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-21413","tags":["US Government Resource"]}],"techniques":[{"id":"T1566.002","name":"Spearphishing Link","tactics":["initial-access"],"provenance":"source","basis":"ctid-kev","bases":["ctid-kev"],"basisDetail":"CTID Mappings Explorer KEV 07/28/2025 (ATT&CK 16.1); capability: Security Feature Bypass","mappingType":"exploitation_technique","evidence":[],"comment":"Attackers can send a specially crafted email that uses the file:// protocol to reference a server that they own, ending the file:// link with an exclamation mark to bypass Outlook's security features, leading to remote code execution.","confidence":"high"},{"id":"T1059","name":"Command and Scripting Interpreter","tactics":["execution"],"provenance":"source","basis":"ctid-kev","bases":["ctid-kev"],"basisDetail":"CTID Mappings Explorer KEV 07/28/2025 (ATT&CK 16.1); capability: Security Feature Bypass","mappingType":"primary_impact","evidence":[],"comment":"Attackers can send a specially crafted email that uses the file:// protocol to reference a server that they own, ending the file:// link with an exclamation mark to bypass Outlook's security features, leading to remote code execution.","confidence":"high"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2024-19122","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2024-19122","exploited":true,"exploitedSince":"2025-02-06","provenance":"source"},"exploits":[],"exploitSources":{"pocGithub":{"count":31,"skipped":11,"earliest":"2024-02-15","earliestUrl":"https://github.com/duy-31/CVE-2024-21413","repos":[{"name":"xaitax/CVE-2024-21413-Microsoft-Outlook-Remote-Code-Execution-Vulnerability","url":"https://github.com/xaitax/CVE-2024-21413-Microsoft-Outlook-Remote-Code-Execution-Vulnerability","stars":780,"created":"2024-02-16"},{"name":"CMNatic/CVE-2024-21413","url":"https://github.com/CMNatic/CVE-2024-21413","stars":294,"created":"2024-02-17"},{"name":"duy-31/CVE-2024-21413","url":"https://github.com/duy-31/CVE-2024-21413","stars":156,"created":"2024-02-15"},{"name":"ThemeHackers/CVE-2024-21413","url":"https://github.com/ThemeHackers/CVE-2024-21413","stars":25,"created":"2024-08-31"},{"name":"r00tb1t/CVE-2024-21413-POC","url":"https://github.com/r00tb1t/CVE-2024-21413-POC","stars":17,"created":"2024-02-16"}]},"first":{"date":"2024-02-15","source":"PoC-in-GitHub","url":"https://github.com/duy-31/CVE-2024-21413"},"provenance":"source"},"exploitRefs":["https://www.vicarius.io/vsociety/posts/cve-2024-21413-critical-monikerlink-vulnerability-affecting-microsoft-outlook-detection-script"],"flow":[{"stage":"exploitation","techniques":["T1566.002"],"provenance":"source"},{"stage":"primary","techniques":["T1059"],"provenance":"source"}],"timeline":[{"date":"2024-02-13","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2024-21413","provenance":"source"},{"date":"2024-02-15","kind":"exploit-public","label":"First public exploit: PoC-in-GitHub","url":"https://github.com/duy-31/CVE-2024-21413","provenance":"source"},{"date":"2024-05-14","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://web-assets.esetstatic.com/wls/en/papers/threat-reports/eset-apt-activity-report-q4-2023-q1-2024.pdf","provenance":"source"},{"date":"2025-02-06","kind":"kev","label":"Added to CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"},{"date":"2025-02-06","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2024-19122","provenance":"source"}],"speed":{"daysToPublicExploit":2,"firstExploitFrom":"PoC-in-GitHub","daysToKev":359},"priority":{"score":69.8,"factors":[{"name":"In a KEV catalog","points":35.0,"detail":"listed in CISA KEV and VulnCheck KEV"},{"name":"Recent KEV listing","points":0.0,"detail":"added 900 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":19.97,"detail":"percentile 0.9986"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":5.0,"detail":"1 NVD reference tagged Exploit; 31 PoC-in-GitHub repos"},{"name":"Mentioned in OTX pulses","points":3.0,"detail":"50 pulses"},{"name":"CVSS severity","points":6.86,"detail":"base score 9.8"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]},"lineage":{"familyId":"fam-class-microsoft-office-cwe-20"}}