{"schema":"threatline.record/2","record":{"id":"CVE-2026-55040","aliases":[],"summary":"Microsoft SharePoint Weak Authentication Vulnerability","details":"Microsoft SharePoint contains a weak authentication vulnerability which allows an unauthorized attacker to bypass a security feature over a network.","categories":["Applications & CMS"],"product":"SharePoint","vendor":"Microsoft","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-55040","source_modified_at":"2026-10-08T18:16:58.104Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Microsoft SharePoint Enterprise Server 2016","vendor":"Microsoft","versions":[{"lessThan":"16.0.5561.1001","status":"affected","version":"16.0.0","versionType":"custom"}],"defaultStatus":null},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-55040","source_modified_at":"2026-10-08T18:16:58.104Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Microsoft SharePoint Server 2019","vendor":"Microsoft","versions":[{"lessThan":"16.0.10417.20175","status":"affected","version":"16.0.0","versionType":"custom"}],"defaultStatus":null},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-55040","source_modified_at":"2026-10-08T18:16:58.104Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Microsoft SharePoint Server Subscription Edition","vendor":"Microsoft","versions":[{"lessThan":"16.0.19725.20434","status":"affected","version":"16.0.0","versionType":"custom"}],"defaultStatus":null}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-55040","source_modified_at":"2026-10-08T18:16:58.104Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Microsoft SharePoint Enterprise Server 2016","ecosystem":null},"version":"16.0.5561.1001","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-55040","source_modified_at":"2026-10-08T18:16:58.104Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Microsoft SharePoint Server 2019","ecosystem":null},"version":"16.0.10417.20175","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-55040","source_modified_at":"2026-10-08T18:16:58.104Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Microsoft SharePoint Server Subscription Edition","ecosystem":null},"version":"16.0.19725.20434","basis":"first unaffected version stated in the CVE record"}],"cvss":9.1,"severity":"Critical","kev":{"listed":true,"date_added":"2026-08-18","due_date":"2026-08-21","required_action":"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.","ransomware_campaign_use":"Unknown","forensic_triage":true},"epss":{"probability":0.69536,"percentile":0.99366,"score_date":"2026-10-23"},"published_at":"2026-07-14T17:09:00.641Z","modified_at":"2026-10-08T18:16:58.104Z","provenance":[{"source":"CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23T17:00:09.9001Z"},{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-55040","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-08T18:16:58.104Z"},{"source":"Nuclei","url":"https://github.com/projectdiscovery/nuclei-templates/blob/main/javascript/cves/2026/CVE-2026-55040.yaml","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":null},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-55040","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CISA KEV","CVE List","Nuclei","EPSS"],"references":[{"source":"CVE List","url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040","tags":["vendor-advisory","patch"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55040","source":"CISA KEV"},{"source":"CVE List","url":"https://www.rapid7.com/blog/post/ra-microsoft-sharepoint-jwt-token-authentication-bypass-cve-2026-55040/","tags":["technical-description"]},{"source":"CVE List","url":"https://github.com/sfewer-r7/CVE-2026-55040","tags":["exploit"]},{"source":"CVE List","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-55040","tags":["government-resource"]}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"active","automatable":"yes","technical_impact":"total","assessed_at":"2026-07-13T00:00:00+00:00"},"exploits":[{"kind":"Scanner template","name":"Microsoft SharePoint Server - JWT Authentication Bypass","source":"Nuclei","url":"https://github.com/projectdiscovery/nuclei-templates/blob/main/javascript/cves/2026/CVE-2026-55040.yaml"}],"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-08T18:16:58.104Z","content_hash":"24bb556cc0dcf7c3d9ad10c44005c642e63d281086a2ad62856a3e64a3fde0ec"}}