{"id":"CVE-2026-56164","kind":"vulnerability","aliases":["CVE-2026-56164"],"related":[],"title":"microsoft sharepoint server: Missing authentication for critical function in Microsoft Office SharePoint allows an unauthorized attacker to…","description":"Microsoft SharePoint contains a missing authentication for critical function vulnerability that allows an unauthorized attacker to elevate privileges over a network.\n\nCISA 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.","summary":"Microsoft SharePoint Server has a missing authentication check on a critical function that lets an unauthenticated network attacker gain elevated privileges. CISA lists it as actively exploited in the wild.","severity":"critical","cvss":9.8,"epss":null,"exploited":true,"exploited_at":"2026-07-14T00:00:00+00:00","products":[{"name":"microsoft sharepoint server","fixed":["16.0.19725.20434"],"affected":"< 16.0.19725.20434","ecosystem":"vendor"},{"name":"microsoft sharepoint server","fixed":[],"affected":"= 2016","ecosystem":"vendor"},{"name":"microsoft sharepoint server","fixed":[],"affected":"= 2019","ecosystem":"vendor"},{"name":"Microsoft SharePoint Server","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["exploited","self-hosted","sharepoint-server","vendor","windows"],"not_affected_if":["sharepoint-online"],"how_to_check":null,"fix":"Apply the Microsoft security update or mitigations for CVE-2026-56164 per vendor instructions and CISA BOD 26-04; if no mitigation exists, discontinue use of the product as CISA directs.","status":"open","published_at":"2026-07-14T00:00:00+00:00","first_seen_at":"2026-10-23T19:11:51+00:00","triaged_at":"2026-10-23T20:33:40+00:00","updated_at":"2026-10-24T00:09:50+00:00","category":"vendor","confidence":0.7,"triage":{"at":"2026-10-23T20:33:40Z","model":"claude-haiku-5-5","output":{"fix":"Apply the Microsoft security update or mitigations for CVE-2026-56164 per vendor instructions and CISA BOD 26-04; if no mitigation exists, discontinue use of the product as CISA directs.","summary":"Microsoft SharePoint Server has a missing authentication check on a critical function that lets an unauthenticated network attacker gain elevated privileges. CISA lists it as actively exploited in the wild.","category":"vendor","who_cares":["sharepoint-server","self-hosted","windows"],"confidence":0.7,"analyst_note":"Sources do not give affected or fixed versions, patch KB, or detection steps; check Microsoft Security Response Center advisory for CVE-2026-56164 and the CISA KEV entry.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["sharepoint-online"],"severity_if_unknown":"high"},"cost_usd":0.000377,"input_tokens":2206,"output_tokens":312,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-04':112C,138C,169C '-2026':18A,21A '-56164':19A,22A '26':111C,137C,168C 'accord':101C 'action':97C 'activ':69B 'adher':165C 'allow':13A,85C 'appli':98C 'applic':135C 'asset':159C 'attack':16A,61B,88C 'authent':5A,50B,79C 'base':116C 'bod':110C,136C,167C 'check':51B 'cisa':65B,95C,108C,125C 'cloud':141C 'complianc':106C 'contain':76C 'critic':7A,54B,81C 'cve':17A,20A 'discontinu':144C 'elev':63B,90C 'ensur':105C,164C 'evalu':157C 'exploit':35B,70B 'exposur':162C 'follow':134C 'forens':127C 'function':8A,55B,82C 'gain':62B 'guidanc':123C,139C 'guidelin':171C 'host':38B 'instruct':104C 'internet':161C 'let':57B 'list':66B 'microsoft':1A,10A,23A,26A,29A,32A,44B,74C 'miss':4A,49B,78C 'mitig':99C,150C 'network':60B,94C 'note':122C,133C 'offic':11A 'patch':170C 'priorit':113C 'privileg':64B,91C 'product':148C 'requir':96C,129C 'respons':155C 'risk':118C 'secur':114C 'see':119C,130C 'self':37B 'self-host':36B 'server':3A,25A,28A,31A,34A,41B,46B 'servic':142C 'sharepoint':2A,12A,24A,27A,30A,33A,40B,45B,75C 'sharepoint-serv':39B 'stakehold':153C 'triag':128C 'unauthent':59B 'unauthor':15A,87C 'unavail':152C 'updat':115C 'url':120C,131C 'use':145C 'vendor':42B,103C 'vulner':83C 'wild':73B 'window':43B","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2026-07-14T00:00:00+00:00","kev":{"dateAdded":"2026-07-14","dueDate":"2026-07-17","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.","knownRansomwareCampaignUse":"Unknown"},"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","cvss_by":"secure@microsoft.com","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2026-56164","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-56164","severity":null,"published_at":"2026-07-14T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:51+00:00","fetched_at":"2026-10-25T14:39:37+00:00","note":null},{"source":"nvd","external_id":"CVE-2026-56164","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-56164","severity":null,"published_at":"2026-07-14T17:17:09+00:00","modified_at":"2026-07-14T21:10:41+00:00","first_seen_at":"2026-10-23T23:44:51+00:00","fetched_at":"2026-10-23T23:44:51+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}