{"id":"CVE-2026-20963","kind":"vulnerability","aliases":["CVE-2026-20963"],"related":[],"title":"microsoft sharepoint server: Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code…","description":"Microsoft SharePoint contains a deserialization of untrusted data vulnerability that allows an unauthorized attacker to execute code over a network.\n\nCISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.","summary":"Microsoft SharePoint has a deserialization of untrusted data flaw that lets an unauthenticated attacker run code over the network. CISA lists it as actively exploited in the wild.","severity":"critical","cvss":9.8,"epss":null,"exploited":true,"exploited_at":"2026-03-18T00:00:00+00:00","products":[{"name":"Microsoft SharePoint","fixed":[],"affected":"","ecosystem":"vendor"},{"name":"microsoft sharepoint server","fixed":["16.0.19127.20442"],"affected":"< 16.0.19127.20442","ecosystem":"vendor"},{"name":"microsoft sharepoint server","fixed":[],"affected":"= 2016","ecosystem":"vendor"},{"name":"microsoft sharepoint server","fixed":[],"affected":"= 2019","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["exploited","microsoft","runtime","self-hosted","sharepoint"],"not_affected_if":["sharepoint-online","unknown"],"how_to_check":null,"fix":"Apply the Microsoft mitigations or patch per vendor instructions; the sources do not name the fixed build.\nIf mitigations are unavailable, CISA says to discontinue use of the product.","status":"open","published_at":"2026-01-13T18:16:24+00:00","first_seen_at":"2026-10-23T19:11:51+00:00","triaged_at":"2026-10-23T20:39:07+00:00","updated_at":"2026-10-23T23:44:51+00:00","category":"runtime","confidence":0.6,"triage":{"at":"2026-10-23T20:39:07Z","model":"claude-haiku-5-5","output":{"fix":"Apply the Microsoft mitigations or patch per vendor instructions; the sources do not name the fixed build.\nIf mitigations are unavailable, CISA says to discontinue use of the product.","reach":"network","summary":"Microsoft SharePoint has a deserialization of untrusted data flaw that lets an unauthenticated attacker run code over the network. CISA lists it as actively exploited in the wild.","category":"runtime","who_cares":["sharepoint","microsoft","self-hosted"],"confidence":0.6,"needs_auth":"no","worst_case":"Unauthenticated attacker runs code on the SharePoint server over the network.","analyst_note":"Find the Microsoft advisory for CVE-2026-20963 to get affected and fixed SharePoint versions and the exact mitigation steps; the sources give neither.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["sharepoint-online","unknown"],"user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"critical"},"cost_usd":0.000438,"input_tokens":2536,"output_tokens":368,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-01':103C '-2026':20A,23A '-20963':21A,24A '22':102C 'action':93C 'activ':66B 'allow':12A,81C 'appli':94C 'applic':100C 'attack':15A,56B,84C 'bod':101C 'cisa':62B,91C 'cloud':106C 'code':18A,58B,87C 'contain':73C 'cve':19A,22A 'data':7A,50B,78C 'deseri':4A,47B,75C 'discontinu':109C 'execut':17A,86C 'exploit':36B,67B 'flaw':51B 'follow':99C 'guidanc':104C 'host':41B 'instruct':98C 'let':53B 'list':63B 'microsoft':1A,9A,25A,27A,30A,33A,37B,43B,71C 'mitig':95C,115C 'network':61B,90C 'offic':10A 'per':96C 'product':113C 'requir':92C 'run':57B 'runtim':38B 'self':40B 'self-host':39B 'server':3A,29A,32A,35A 'servic':107C 'sharepoint':2A,11A,26A,28A,31A,34A,42B,44B,72C 'unauthent':55B 'unauthor':14A,83C 'unavail':117C 'untrust':6A,49B,77C 'use':110C 'vendor':97C 'vulner':79C 'wild':70B","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2026-01-13T18:16:24+00:00","kev":{"dateAdded":"2026-03-18","dueDate":"2026-03-21","requiredAction":"Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.","knownRansomwareCampaignUse":"Unknown"},"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvss_by":"secure@microsoft.com","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2026-20963","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-20963","severity":null,"published_at":"2026-03-18T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:51+00:00","fetched_at":"2026-10-25T10:39:04+00:00","note":null},{"source":"nvd","external_id":"CVE-2026-20963","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-20963","severity":null,"published_at":"2026-01-13T18:16:24+00:00","modified_at":"2026-06-17T10:18:07+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"}