{"id":"CVE-2026-55040","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-55040","generatedAt":"2026-10-31T04:55:41.320Z","title":"Microsoft SharePoint Weak Authentication Vulnerability","description":"Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.","published":"2026-07-14T18:18:15.000Z","lastModified":"2026-08-19T04:17:24.000Z","status":"Analyzed","sourceIdentifier":"secure@microsoft.com","cvss":{"version":"3.1","score":9.1,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},"cwe":["CWE-1390"],"affected":["microsoft/sharepoint server"],"epss":{"score":0.69536,"percentile":0.99362,"date":"2026-10-30","history":[{"date":"2026-09-24","score":0.17535,"percentile":0.97031},{"date":"2026-10-05","score":0.69536,"percentile":0.99347}]},"kev":{"listed":true,"dateAdded":"2026-08-18","dueDate":"2026-08-21","knownRansomwareCampaignUse":"Unknown","notes":"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.\nhttps://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"},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"urgent","text":"Known to be exploited in the wild (CISA KEV, CISA remediation deadline 21 August 2026). Treat as an emergency change: patch or isolate now, then hunt for prior compromise."},"changes":[{"kind":"epss","label":"EPSS jump","at":"2026-10-05T00:00:00.000Z","detail":{"to":0.69536,"from":0.17535,"percentile":0.99347},"summary":"EPSS moved from 17.5% to 69.5% probability of exploitation in the next thirty days."},{"kind":"epss","label":"EPSS jump","at":"2026-09-24T00:00:00.000Z","detail":{"to":0.17535,"from":0.50585,"percentile":0.97031},"summary":"EPSS moved from 50.6% to 17.5% probability of exploitation in the next thirty days."}],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040","tags":["Patch","Vendor Advisory"],"source":"secure@microsoft.com"},{"url":"https://github.com/sfewer-r7/CVE-2026-55040","tags":["Exploit"],"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-55040","tags":["Exploit","Third Party Advisory"],"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://www.rapid7.com/blog/post/ra-microsoft-sharepoint-jwt-token-authentication-bypass-cve-2026-55040/","tags":["US Government Resource"],"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-55040","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}