{"id":"CVE-2026-58644","kind":"vulnerability","aliases":["CVE-2026-58644"],"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 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 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":"2026-07-16T00:00:00+00:00","products":[{"name":"Microsoft SharePoint","fixed":[],"affected":"","ecosystem":"vendor"},{"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"}],"ecosystems":["vendor"],"tags":["exploited","microsoft","self-hosted","sharepoint","vendor"],"not_affected_if":["managed-hosting","sharepoint-online"],"how_to_check":null,"fix":"Apply the mitigations and patch from Microsoft's advisory for CVE-2026-58644 as directed by CISA BOD 26-04; if no mitigation exists, discontinue use of the affected SharePoint product.","status":"open","published_at":"2026-07-14T17:17:14+00:00","first_seen_at":"2026-10-23T19:11:51+00:00","triaged_at":"2026-10-23T20:33:37+00:00","updated_at":"2026-10-23T23:44:51+00:00","category":"vendor","confidence":0.6,"triage":{"at":"2026-10-23T20:33:37Z","model":"claude-haiku-5-5","output":{"fix":"Apply the mitigations and patch from Microsoft's advisory for CVE-2026-58644 as directed by CISA BOD 26-04; if no mitigation exists, discontinue use of the affected SharePoint product.","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":"vendor","who_cares":["sharepoint","self-hosted","microsoft"],"confidence":0.6,"analyst_note":"Sources do not list affected or fixed SharePoint versions or patch IDs; find the Microsoft MSRC advisory for CVE-2026-58644 and the CISA KEV entry for exact versions and mitigations.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["managed-hosting","sharepoint-online"],"severity_if_unknown":"critical"},"cost_usd":0.000383,"input_tokens":2198,"output_tokens":327,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-04':108C,134C,165C '-2026':20A,23A '-58644':21A,24A '26':107C,133C,164C 'accord':97C 'action':93C 'activ':66B 'adher':161C 'allow':12A,81C 'appli':94C 'applic':131C 'asset':155C 'attack':15A,56B,84C 'base':112C 'bod':106C,132C,163C 'cisa':62B,91C,104C,121C 'cloud':137C 'code':18A,58B,87C 'complianc':102C 'contain':73C 'cve':19A,22A 'data':7A,50B,78C 'deseri':4A,47B,75C 'discontinu':140C 'ensur':101C,160C 'evalu':153C 'execut':17A,86C 'exploit':36B,67B 'exposur':158C 'flaw':51B 'follow':130C 'forens':123C 'guidanc':119C,135C 'guidelin':167C 'host':40B 'instruct':100C 'internet':157C 'let':53B 'list':63B 'microsoft':1A,9A,25A,27A,30A,33A,37B,43B,71C 'mitig':95C,146C 'network':61B,90C 'note':118C,129C 'offic':10A 'patch':166C 'priorit':109C 'product':144C 'requir':92C,125C 'respons':151C 'risk':114C 'run':57B 'secur':110C 'see':115C,126C 'self':39B 'self-host':38B 'server':3A,29A,32A,35A 'servic':138C 'sharepoint':2A,11A,26A,28A,31A,34A,41B,44B,72C 'stakehold':149C 'triag':124C 'unauthent':55B 'unauthor':14A,83C 'unavail':148C 'untrust':6A,49B,77C 'updat':111C 'url':116C,127C 'use':141C 'vendor':42B,99C 'vulner':79C 'wild':70B","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2026-07-14T17:17:14+00:00","kev":{"dateAdded":"2026-07-16","dueDate":"2026-07-19","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:H/I:H/A:H","cvss_by":"secure@microsoft.com","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2026-58644","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-58644","severity":null,"published_at":"2026-07-16T00:00:00+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-2026-58644","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-58644","severity":null,"published_at":"2026-07-14T17:17:14+00:00","modified_at":"2026-07-17T05:16:40+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"}