{"id":"CVE-2025-21333","kind":"vulnerability","aliases":["CVE-2025-21333"],"related":[],"title":"Windows Hyper-V NT Kernel Integration VSP Elevation of Privilege Vulnerability","description":"Microsoft Windows Hyper-V NT Kernel Integration VSP contains a heap-based buffer overflow vulnerability that allows a local attacker to gain SYSTEM privileges.\n\nCISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.","summary":"A heap-based buffer overflow in the Windows Hyper-V NT Kernel Integration VSP lets a local attacker escalate to SYSTEM privileges. It is listed in CISA's Known Exploited Vulnerabilities catalog, so it is being used in real attacks.","severity":"high","cvss":7.8,"epss":null,"exploited":true,"exploited_at":"2025-01-14T00:00:00+00:00","products":[{"name":"Microsoft Windows","fixed":[],"affected":"","ecosystem":"vendor"},{"name":"microsoft windows 10 21h2","fixed":["10.0.19044.5371"],"affected":"< 10.0.19044.5371","ecosystem":"vendor"},{"name":"microsoft windows 10 22h2","fixed":["10.0.19045.5371"],"affected":"< 10.0.19045.5371","ecosystem":"vendor"},{"name":"microsoft windows 11 22h2","fixed":["10.0.22621.4751"],"affected":"< 10.0.22621.4751","ecosystem":"vendor"},{"name":"microsoft windows 11 23h2","fixed":["10.0.22631.4751"],"affected":"< 10.0.22631.4751","ecosystem":"vendor"},{"name":"microsoft windows 11 24h2","fixed":["10.0.26100.2894"],"affected":"< 10.0.26100.2894","ecosystem":"vendor"},{"name":"microsoft windows server 2022 23h2","fixed":["10.0.25398.1369"],"affected":"< 10.0.25398.1369","ecosystem":"vendor"},{"name":"microsoft windows server 2025","fixed":["10.0.26100.2894"],"affected":"< 10.0.26100.2894","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["exploited","hyper-v","infrastructure","windows"],"not_affected_if":["hyper-v-not-enabled"],"how_to_check":null,"fix":"Apply the Microsoft security update for CVE-2025-21333 per vendor instructions, or discontinue use of the product if mitigations are unavailable.","status":"open","published_at":"2025-01-14T00:00:00+00:00","first_seen_at":"2026-10-23T19:11:51+00:00","triaged_at":"2026-10-23T20:52:43+00:00","updated_at":"2026-10-23T22:29:05+00:00","category":"infrastructure","confidence":0.7,"triage":{"at":"2026-10-23T20:52:43Z","model":"claude-haiku-5-5","output":{"fix":"Apply the Microsoft security update for CVE-2025-21333 per vendor instructions, or discontinue use of the product if mitigations are unavailable.","reach":"local","impact":"high","summary":"A heap-based buffer overflow in the Windows Hyper-V NT Kernel Integration VSP lets a local attacker escalate to SYSTEM privileges. It is listed in CISA's Known Exploited Vulnerabilities catalog, so it is being used in real attacks.","category":"infrastructure","who_cares":["windows","hyper-v"],"confidence":0.7,"needs_auth":"yes","worst_case":"local attacker gains SYSTEM privileges on the Windows host","analyst_note":"Find the affected Windows builds and the patch KB numbers in Microsoft's CVE-2025-21333 advisory, and confirm the Hyper-V role requirement.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["hyper-v-not-enabled"],"user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"high"},"cost_usd":0.000457,"input_tokens":2657,"output_tokens":382,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2025':14A,17A '-21333':15A,18A '10':23A,27A '11':31A,35A,39A '2022':44A '2025':49A '21h2':24A '22h2':28A,32A '23h2':36A,45A '24h2':40A 'action':126C 'allow':116C 'appli':127C 'attack':75B,97B,119C 'base':59B,111C 'buffer':60B,112C 'catalog':89B 'cisa':84B,124C 'contain':107C 'cve':13A,16A 'discontinu':133C 'elev':9A 'escal':76B 'exploit':50B,87B 'gain':121C 'heap':58B,110C 'heap-bas':57B,109C 'hyper':3A,52B,66B,101C 'hyper-v':2A,51B,65B,100C 'infrastructur':54B 'instruct':131C 'integr':7A,70B,105C 'kernel':6A,69B,104C 'known':86B 'let':72B 'list':82B 'local':74B,118C 'microsoft':19A,21A,25A,29A,33A,37A,41A,46A,98C 'mitig':128C,139C 'nt':5A,68B,103C 'overflow':61B,113C 'per':129C 'privileg':11A,79B,123C 'product':137C 'real':96B 'requir':125C 'server':43A,48A 'system':78B,122C 'unavail':141C 'use':94B,134C 'v':4A,53B,67B,102C 'vendor':130C 'vsp':8A,71B,106C 'vulner':12A,88B,114C 'window':1A,55B,64B,99C 'windows':20A,22A,26A,30A,34A,38A,42A,47A","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2025-01-14T00:00:00+00:00","kev":{"dateAdded":"2025-01-14","dueDate":"2025-02-04","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:H/I:H/A:H","cvss_by":"secure@microsoft.com","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2025-21333","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2025-21333","severity":null,"published_at":"2025-01-14T00:00:00+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-2025-21333","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-21333","severity":null,"published_at":"2025-01-14T18:15:58+00:00","modified_at":"2026-06-17T08:43:07+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"}