{"id":"CVE-2025-21391","kind":"vulnerability","aliases":["CVE-2025-21391"],"related":[],"title":"Windows Storage Elevation of Privilege Vulnerability","description":"Microsoft Windows Storage contains a link following vulnerability that could allow for privilege escalation. This vulnerability could allow an attacker to delete data including data that results in the service being unavailable.\n\nCISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.","summary":"A link-following flaw in the Windows Storage component lets a local attacker redirect file operations to protected targets. An attacker can use it to escalate privileges and delete data, which can make the service unavailable.","severity":"high","cvss":7.1,"epss":null,"exploited":true,"exploited_at":"2025-02-11T00:00:00+00:00","products":[{"name":"Microsoft Windows","fixed":[],"affected":"","ecosystem":"vendor"},{"name":"microsoft windows 10 1507","fixed":["10.0.10240.20915"],"affected":"< 10.0.10240.20915","ecosystem":"vendor"},{"name":"microsoft windows 10 1607","fixed":["10.0.14393.7785"],"affected":"< 10.0.14393.7785","ecosystem":"vendor"},{"name":"microsoft windows 10 1809","fixed":["10.0.17763.6893"],"affected":"< 10.0.17763.6893","ecosystem":"vendor"},{"name":"microsoft windows 10 21h2","fixed":["10.0.19044.5487"],"affected":"< 10.0.19044.5487","ecosystem":"vendor"},{"name":"microsoft windows 10 22h2","fixed":["10.0.19045.5487"],"affected":"< 10.0.19045.5487","ecosystem":"vendor"},{"name":"microsoft windows 11 22h2","fixed":["10.0.22621.4890"],"affected":"< 10.0.22621.4890","ecosystem":"vendor"},{"name":"microsoft windows 11 23h2","fixed":["10.0.22631.4890"],"affected":"< 10.0.22631.4890","ecosystem":"vendor"},{"name":"microsoft windows 11 24h2","fixed":["10.0.26100.3107"],"affected":"< 10.0.26100.3107","ecosystem":"vendor"},{"name":"microsoft windows server 2016","fixed":["10.0.14393.7785"],"affected":"< 10.0.14393.7785","ecosystem":"vendor"},{"name":"microsoft windows server 2019","fixed":["10.0.17763.6893"],"affected":"< 10.0.17763.6893","ecosystem":"vendor"},{"name":"microsoft windows server 2022","fixed":["10.0.20348.3148"],"affected":"< 10.0.20348.3148","ecosystem":"vendor"},{"name":"microsoft windows server 2022 23h2","fixed":["10.0.25398.1425"],"affected":"< 10.0.25398.1425","ecosystem":"vendor"},{"name":"microsoft windows server 2025","fixed":["10.0.26100.3107"],"affected":"< 10.0.26100.3107","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["exploited","infrastructure","windows","windows-server"],"not_affected_if":["unknown"],"how_to_check":null,"fix":"Apply the Microsoft update for CVE-2025-21391 per vendor instructions; the CISA entry says to discontinue use if mitigations are unavailable.\nFixed version numbers are not in the sources.","status":"open","published_at":"2025-02-11T00:00:00+00:00","first_seen_at":"2026-10-23T19:11:51+00:00","triaged_at":"2026-10-23T20:52:27+00:00","updated_at":"2026-10-23T22:29:05+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-23T20:52:27Z","model":"claude-haiku-5-5","output":{"fix":"Apply the Microsoft update for CVE-2025-21391 per vendor instructions; the CISA entry says to discontinue use if mitigations are unavailable.\nFixed version numbers are not in the sources.","reach":"local","impact":"high","summary":"A link-following flaw in the Windows Storage component lets a local attacker redirect file operations to protected targets. An attacker can use it to escalate privileges and delete data, which can make the service unavailable.","category":"infrastructure","who_cares":["windows","windows-server"],"confidence":0.6,"needs_auth":"yes","worst_case":"local user escalates privileges and deletes data, causing outage","analyst_note":"Find the Microsoft advisory for CVE-2025-21391 to get affected builds, fixed KB numbers and any mitigation steps; the sources give none.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["unknown"],"user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000442,"input_tokens":2631,"output_tokens":357,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2025':8A,11A '-21391':9A,12A '10':17A,21A,25A,29A,33A '11':37A,41A,45A '1507':18A '1607':22A '1809':26A '2016':50A '2019':54A '2022':58A,62A '2025':67A '21h2':30A '22h2':34A,38A '23h2':42A,63A '24h2':46A 'action':145C 'allow':121C,128C 'appli':146C 'attack':87B,95B,130C 'cisa':143C 'compon':83B 'contain':114C 'could':120C,127C 'cve':7A,10A 'data':104B,133C,135C 'delet':103B,132C 'discontinu':152C 'elev':3A 'escal':100B,124C 'exploit':68B 'file':89B 'flaw':78B 'follow':77B,117C 'includ':134C 'infrastructur':69B 'instruct':150C 'let':84B 'link':76B,116C 'link-follow':75B 'local':86B 'make':107B 'microsoft':13A,15A,19A,23A,27A,31A,35A,39A,43A,47A,51A,55A,59A,64A,111C 'mitig':147C,158C 'oper':90B 'per':148C 'privileg':5A,101B,123C 'product':156C 'protect':92B 'redirect':88B 'requir':144C 'result':137C 'server':49A,53A,57A,61A,66A,73B 'servic':109B,140C 'storag':2A,82B,113C 'target':93B 'unavail':110B,142C,160C 'use':97B,153C 'vendor':149C 'vulner':6A,118C,126C 'window':1A,70B,72B,81B,112C 'windows':14A,16A,20A,24A,28A,32A,36A,40A,44A,48A,52A,56A,60A,65A 'windows-serv':71B","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2025-02-11T00:00:00+00:00","kev":{"dateAdded":"2025-02-11","dueDate":"2025-03-04","requiredAction":"Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.","knownRansomwareCampaignUse":"Unknown"},"cvss_vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H","cvss_by":"secure@microsoft.com","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2025-21391","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2025-21391","severity":null,"published_at":"2025-02-11T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:51+00:00","fetched_at":"2026-10-25T12:39:22+00:00","note":null},{"source":"nvd","external_id":"CVE-2025-21391","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-21391","severity":null,"published_at":"2025-02-11T18:15:37+00:00","modified_at":"2026-09-24T13:10:00+00:00","first_seen_at":"2026-10-23T22:29:05+00:00","fetched_at":"2026-10-23T22:29:05+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"}