{"id":"CVE-2026-98718","kind":"vulnerability","aliases":["CVE-2026-98718"],"related":[],"title":"Linux KVM: cache flush ordering lets reclaimed SEV guest memory corrupt host pages","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SEV: Do cache maintenance on the source VM *before* clearing SEV state\n\nExplicitly flush caches after intra-host migration before clearing \"SEV\nactive\" on the source VM, as doing cache maintenance afterwards creates a\ntiny window where memory reclaim could return memory to the host without\nperforming a cache flush, e.g. as pointed out by Sashiko:\n\n  CPU1 in sev_migrate_from():\n    src->active = false;\n\n  CPU2 running concurrent unmap:\n    Since active is false, the automatic cache flush in\n    sev_guest_memory_reclaimed is skipped.\n    The host frees and reallocates the page.\n\n  CPU1 in sev_migrate_from():\n    sev_writeback_caches(src_kvm);\n    Executes a hardware cache flush (wbnoinvd), which writes the guest's old\n    dirty ciphertext over the new page owner's data.","summary":"In the Linux kernel's KVM SEV code, the source VM's caches were flushed after its SEV active state was cleared during intra-host migration, leaving a race window. A reclaimed page could receive stale encrypted guest data written over the new owner's contents.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["amd-sev","hypervisor","kvm","linux","runtime"],"not_affected_if":["no-amd-sev-guests","no-kvm"],"how_to_check":"- unknown","fix":"- Update the Linux kernel to a release that includes the upstream fix (the sources do not name a version).","status":"open","published_at":"2026-10-18T16:17:25+00:00","first_seen_at":"2026-10-23T21:57:16+00:00","triaged_at":"2026-10-25T05:17:27+00:00","updated_at":"2026-10-25T05:17:27+00:00","category":"runtime","confidence":0.5,"triage":{"at":"2026-10-25T05:17:27Z","model":"claude-haiku-5-5","output":{"fix":"- Update the Linux kernel to a release that includes the upstream fix (the sources do not name a version).","reach":"local","title":"Linux KVM: cache flush ordering lets reclaimed SEV guest memory corrupt host pages","impact":"medium","summary":"In the Linux kernel's KVM SEV code, the source VM's caches were flushed after its SEV active state was cleared during intra-host migration, leaving a race window. A reclaimed page could receive stale encrypted guest data written over the new owner's contents.","category":"runtime","nicknames":[],"who_cares":["linux","kvm","amd-sev","hypervisor"],"confidence":0.5,"needs_auth":"unknown","worst_case":"Host memory corrupted with stale guest ciphertext, possibly affecting other tenants.","analyst_note":"Check the NVD entry and the upstream kernel commit for the fixed kernel versions and the affected version range.","how_to_check":"- unknown","needs_analyst":true,"not_affected_if":["no-amd-sev-guests","no-kvm"],"who_is_affected":"Hosts running Linux KVM with AMD SEV or SEV-ES guests that perform intra-host migration are the systems concerned. Hosts without AMD SEV guests, or without KVM, are not affected.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"low"},"cost_usd":0.000596,"input_tokens":3542,"output_tokens":483,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2026':15A,18A '-98718':16A,19A 'activ':45B,108C,148C,155C 'afterward':117C 'amd':21B 'amd-sev':20B 'automat':159C 'cach':3A,39B,87C,99C,115C,134C,160C,183C,189C 'ciphertext':199C 'clear':48B,94C,106C 'code':34B 'concurr':152C 'content':73B 'corrupt':11A 'could':61B,125C 'cpu1':142C,176C 'cpu2':150C 'creat':118C 'cve':14A,17A 'data':66B,206C 'dirti':198C 'e.g':136C 'encrypt':64B 'execut':186C 'explicit':97C 'fals':149C,157C 'flush':4A,41B,98C,135C,161C,190C 'follow':79C 'free':171C 'guest':9A,65B,164C,195C 'hardwar':188C 'host':12A,52B,103C,130C,170C 'hypervisor':23B 'intra':51B,102C 'intra-host':50B,101C 'kernel':30B,77C 'kvm':2A,24B,32B,84C,185C 'leav':54B 'let':6A 'linux':1A,25B,29B,76C 'mainten':88C,116C 'memori':10A,123C,127C,165C 'migrat':53B,104C,145C,179C 'new':70B,202C 'old':197C 'order':5A 'owner':71B,204C 'page':13A,60B,175C,203C 'perform':132C 'point':138C 'race':56B 'realloc':173C 'receiv':62B 'reclaim':7A,59B,124C,166C 'resolv':83C 'return':126C 'run':151C 'runtim':26B 'sashiko':141C 'sev':8A,22B,33B,44B,85C,95C,107C,144C,163C,178C,181C 'sinc':154C 'skip':168C 'sourc':36B,91C,111C 'src':147C,184C 'stale':63B 'state':46B,96C 'tini':120C 'unmap':153C 'vm':37B,92C,112C 'vulner':80C 'wbnoinvd':191C 'window':57B,121C 'without':131C 'write':193C 'writeback':182C 'written':67B","nicknames":[],"mitigations":[],"who_affected":"Hosts running Linux KVM with AMD SEV or SEV-ES guests that perform intra-host migration are the systems concerned. Hosts without AMD SEV guests, or without KVM, are not affected.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-18T16:17:25+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-98718","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98718","severity":null,"published_at":"2026-10-18T16:17:25+00:00","modified_at":"2026-10-19T10:19:36+00:00","first_seen_at":"2026-10-23T21:57:16+00:00","fetched_at":"2026-10-23T22:28:56+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"}