{"id":"CVE-2025-64394","kind":"vulnerability","aliases":["CVE-2025-64394"],"related":[],"title":"Veeam Backup for Microsoft 365: local users can write files as SYSTEM","description":"A vulnerability allowing a low-privileged local user to write arbitrary files with SYSTEM privileges during the installation of Veeam Backup for Microsoft 365, which can lead to privilege escalation or denial of service.","summary":"During installation of Veeam Backup for Microsoft 365, a low-privileged local user can write arbitrary files with SYSTEM privileges. An attacker can use this to escalate privileges to SYSTEM or crash the service.","severity":"medium","cvss":4.3,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["backup","infrastructure","veeam","windows"],"not_affected_if":["no-local-untrusted-users"],"how_to_check":"- Check the installed Veeam Backup for Microsoft 365 version in Programs and Features or the product's About page\n- unknown","fix":"- Update Veeam Backup for Microsoft 365 to a fixed build from Veeam's advisory\n- unknown","status":"open","published_at":"2026-10-27T17:16:53+00:00","first_seen_at":"2026-10-27T17:32:44+00:00","triaged_at":"2026-10-27T17:34:59+00:00","updated_at":"2026-10-27T17:34:59+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-27T17:34:59Z","model":"claude-haiku-5-5","output":{"fix":"- Update Veeam Backup for Microsoft 365 to a fixed build from Veeam's advisory\n- unknown","reach":"local","title":"Veeam Backup for Microsoft 365: local users can write files as SYSTEM","impact":"high","summary":"During installation of Veeam Backup for Microsoft 365, a low-privileged local user can write arbitrary files with SYSTEM privileges. An attacker can use this to escalate privileges to SYSTEM or crash the service.","category":"infrastructure","nicknames":[],"who_cares":["windows","veeam","backup"],"confidence":0.6,"needs_auth":"yes","worst_case":"local user gains SYSTEM privileges on the backup server","analyst_note":"Find the Veeam advisory for CVE-2025-64394 to get affected and fixed build numbers.","how_to_check":"- Check the installed Veeam Backup for Microsoft 365 version in Programs and Features or the product's About page\n- unknown","needs_analyst":true,"not_affected_if":["no-local-untrusted-users"],"who_is_affected":"Hosts running Veeam Backup for Microsoft 365 on Windows where local, non-admin users can log on. The sources do not name the affected versions. Teams that do not run this product on shared or multi-user Windows machines can skip it.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"medium"},"cost_usd":0.000576,"input_tokens":3291,"output_tokens":494,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-2025':14A,17A '-64394':15A,18A '365':5A,30B,82C 'allow':60C 'arbitrari':39B,69C 'attack':45B 'backup':2A,19B,27B,79C 'crash':55B 'cve':13A,16A 'denial':90C 'escal':50B,88C 'file':10A,40B,70C 'infrastructur':20B 'instal':24B,76C 'lead':85C 'local':6A,35B,65C 'low':33B,63C 'low-privileg':32B,62C 'microsoft':4A,29B,81C 'privileg':34B,43B,51B,64C,73C,87C 'servic':57B,92C 'system':12A,42B,53B,72C 'use':47B 'user':7A,36B,66C 'veeam':1A,21B,26B,78C 'vulner':59C 'window':22B 'write':9A,38B,68C","nicknames":[],"mitigations":[],"who_affected":"Hosts running Veeam Backup for Microsoft 365 on Windows where local, non-admin users can log on. The sources do not name the affected versions. Teams that do not run this product on shared or multi-user Windows machines can skip it.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-27T17:16:53+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:A/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"support@hackerone.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2025-64394","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-64394","severity":null,"published_at":"2026-10-27T17:16:53+00:00","modified_at":"2026-10-27T17:16:53+00:00","first_seen_at":"2026-10-27T17:32:44+00:00","fetched_at":"2026-10-27T17:32:44+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"}