{"id":"CVE-2026-55040","published":"2026-07-14T18:18:15Z","modified":"2026-08-19T04:17:23Z","title":"Microsoft SharePoint Weak Authentication Vulnerability","vendor":"Microsoft","product":"SharePoint","tier":"core","eol":null,"description":{"text":"Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.","provenance":"source","from":"NVD"},"summary":{"text":"Microsoft SharePoint contains a weak authentication flaw in Microsoft Office SharePoint, a weakness classified as Weak Authentication. An unauthorized attacker over the network can bypass a security feature of the product, with no privileges, no user interaction, and no special configuration required.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:10:10Z"},"cvss":{"score":9.1,"severity":"CRITICAL","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","provenance":"source","from":"NVD"},"epss":{"score":0.69536,"percentile":0.99362,"date":"2026-10-30","provenance":"source"},"kev":{"dateAdded":"2026-08-18","dueDate":"2026-08-21","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-2026-55040 ; 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-2026-55040","provenance":"source"},"vulncheckKev":{"dateAdded":"2026-08-12","exploitedFirstSeen":"2026-08-12","ransomware":false,"evidence":[{"url":"https://previdian.com/CVE-2026-55040","date":"2026-08-12"},{"url":"https://x.com/DefusedCyber/status/2087456962896093522","date":"2026-08-12"},{"url":"https://x.com/UK_Daniel_Card/status/2087508182868324424","date":"2026-08-12"},{"url":"https://cydome.io/maritime-cybersecurity-bulletin-august-14th-2026/","date":"2026-08-14"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2026-08-18"},{"url":"https://x.com/DefusedCyber/status/2092228764323217723","date":"2026-08-25"},{"url":"https://www.recordedfuture.com/blog/august-2026-cve-landscape","date":"2026-09-08"}],"evidenceTotal":7,"provenance":"source"},"exploited":true,"otx":{"pulseCount":50,"pulses":[{"name":"Actively_Exploited_Kev | Oct 31, 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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-1390","name":"Weak Authentication"}],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040","tags":["Patch","Vendor Advisory"]},{"url":"https://github.com/sfewer-r7/CVE-2026-55040","tags":["Exploit"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-55040","tags":["Exploit","Third Party Advisory"]},{"url":"https://www.rapid7.com/blog/post/ra-microsoft-sharepoint-jwt-token-authentication-bypass-cve-2026-55040/","tags":["US Government Resource"]}],"techniques":[{"id":"T1190","name":"Exploit Public-Facing 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from the description (quote-validated, not expert-reviewed)"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2026-44211","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-44211","exploited":true,"exploitedSince":"2026-08-18","provenance":"source"},"exploits":[],"exploitSources":{"pocGithub":{"count":4,"skipped":1,"earliest":"2026-07-28","earliestUrl":"https://github.com/l0ggg/CVE-2026-55040","repos":[{"name":"sfewer-r7/CVE-2026-55040","url":"https://github.com/sfewer-r7/CVE-2026-55040","stars":59,"created":"2026-08-06"},{"name":"l0ggg/CVE-2026-55040","url":"https://github.com/l0ggg/CVE-2026-55040","stars":3,"created":"2026-07-28"},{"name":"maxprog-svg/CVE-2026-55040-Mass-Exploit","url":"https://github.com/maxprog-svg/CVE-2026-55040-Mass-Exploit","stars":0,"created":"2026-08-27"},{"name":"virologi-info/mssharepoint-scanner","url":"https://github.com/virologi-info/mssharepoint-scanner","stars":0,"created":"2026-08-27"}]},"nuclei":[{"id":"CVE-2026-55040","name":"Microsoft SharePoint Server - JWT 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