{"id":"CVE-2026-58644","published":"2026-07-14T17:17:14Z","modified":"2026-07-17T05:16:40Z","title":"Microsoft SharePoint Deserialization of Untrusted Data Vulnerability","vendor":"Microsoft","product":"SharePoint","tier":"core","eol":null,"description":{"text":"Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.","provenance":"source","from":"NVD"},"summary":{"text":"Microsoft SharePoint contains a deserialization of untrusted data flaw in its Microsoft Office SharePoint component. An unauthorized attacker can exploit it over a network to execute code, with no authentication or user interaction required and a low-complexity attack.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:12:19Z"},"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":0.15873,"percentile":0.96883,"date":"2026-10-30","provenance":"source"},"kev":{"dateAdded":"2026-07-16","dueDate":"2026-07-19","ransomware":false,"requiredAction":"Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.","notes":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-58644 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-58644","provenance":"source"},"vulncheckKev":{"dateAdded":"2026-07-14","exploitedFirstSeen":"2026-07-14","ransomware":false,"evidence":[{"url":"https://api.msrc.microsoft.com/cvrf/v3.0/cvrf/2026-Jul","date":"2026-07-14"},{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-58644","date":"2026-07-14"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2026-07-16"},{"url":"https://www.rapid7.com/blog/post/etr-cve-2026-58644-microsoft-sharepoint-server-unauthenticated-remote-code-execution-vulnerability-exploited-in-the-wild/","date":"2026-07-17"},{"url":"https://www.resecurity.com/es/blog/article/from-web-request-to-domain-compromise-understanding-the-july-2026-sharepoint-attacks","date":"2026-07-18"},{"url":"https://blog.hunterstrategy.net/the-convenience-problem/","date":"2026-07-24"},{"url":"https://www.recordedfuture.com/blog/july-2026-cve-landscape","date":"2026-08-07"},{"url":"https://www.acn.gov.it/portale/documents/20119/1300791/Operational_Summary_lug26_CLEAR.pdf/88b05799-3e4c-f3ed-4a42-d9e68e080604?t=1787220905144","date":"2026-08-20"}],"evidenceTotal":8,"provenance":"source"},"exploited":true,"otx":{"pulseCount":50,"pulses":[{"name":"Actively_Exploited_Kev | Oct 31, 2026","url":"https://otx.alienvault.com/pulse/6ae4aefab0c2191cecd41862","created":"2026-10-30"},{"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"}],"provenance":"machine"},"cwes":[{"id":"CWE-502","name":"Deserialization of Untrusted Data"}],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-58644","tags":["Patch","Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-58644","tags":["US Government Resource"]}],"techniques":[{"id":"T1190","name":"Exploit Public-Facing Application","tactics":["initial-access"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: Unauthenticated network exploitation of public-facing SharePoint server","mappingType":"exploitation_technique","evidence":[{"from":"description","quote":"allows an unauthorized attacker to execute code over a network","start":65,"end":127}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"},{"id":"T1059","name":"Command and Scripting Interpreter","tactics":["execution"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: Deserialization flaw yields arbitrary code execution","mappingType":"primary_impact","evidence":[{"from":"description","quote":"allows an unauthorized attacker to execute code over a network","start":65,"end":127}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2026-43779","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-43779","exploited":true,"exploitedSince":"2026-07-16","provenance":"source"},"exploits":[],"exploitSources":{"nuclei":[{"id":"CVE-2026-58644","name":"Microsoft SharePoint Server - WS-Federation BinaryFormatter Deserialization RCE","severity":"critical","path":"http/cves/2026/CVE-2026-58644.yaml","url":"https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-58644.yaml"}],"provenance":"source"},"exploitRefs":[],"flow":[{"stage":"exploitation","techniques":["T1190"],"provenance":"ai"},{"stage":"primary","techniques":["T1059"],"provenance":"ai"}],"timeline":[{"date":"2026-07-14","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-58644","provenance":"source"},{"date":"2026-07-14","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://api.msrc.microsoft.com/cvrf/v3.0/cvrf/2026-Jul","provenance":"source"},{"date":"2026-07-16","kind":"kev","label":"Added to CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"},{"date":"2026-07-16","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-43779","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":null,"daysToKev":2},"priority":{"score":74.2,"factors":[{"name":"In a KEV catalog","points":35.0,"detail":"listed in CISA KEV and VulnCheck KEV"},{"name":"Recent KEV listing","points":5.0,"detail":"added 109 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":19.38,"detail":"percentile 0.9688"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":5.0,"detail":"1 nuclei template"},{"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-sharepoint-cwe-502"}}