{"id":"CVE-2026-98716","kind":"vulnerability","aliases":["CVE-2026-98716"],"related":[],"title":"Linux KVM: SVM checks wrong MSR bitmap for nested guests","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SVM: Use the active VMCB's MSR bitmap when checking if MSR is intercepted\n\nUse the MSR permission bitmap of the active VMCB instead of assuming that\nKVM is always using vmcb02's bitmap when L2 is active, as KVM uses msrpm02\nif and only if L1 wants to intercept MSR accesses, i.e. if and only if KVM\nneeds to merge msprm01 with msrpm12.\n\nDon't bother tracking the virtual address of the bitmap that's being used,\nas __va() is cheap on x86, and caching the virtual address would introduce\nyet another source of potentially stale information.","summary":"The Linux kernel's KVM module on AMD SVM hosts can consult the wrong MSR permission bitmap when a nested guest (L2) is running, because it assumes the bitmap of vmcb02 is always active. The description does not state what an attacker gains or how the mismatch is exploited.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["amd-svm","kvm","linux-kernel","nested-virtualization","runtime"],"not_affected_if":["no-kvm-on-amd","no-nested-virtualization"],"how_to_check":"- unknown","fix":"- unknown","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":0.3,"triage":{"at":"2026-10-25T05:17:27Z","model":"claude-haiku-5-5","output":{"fix":"- unknown","reach":"unknown","title":"Linux KVM: SVM checks wrong MSR bitmap for nested guests","impact":"medium","summary":"The Linux kernel's KVM module on AMD SVM hosts can consult the wrong MSR permission bitmap when a nested guest (L2) is running, because it assumes the bitmap of vmcb02 is always active. The description does not state what an attacker gains or how the mismatch is exploited.","category":"runtime","nicknames":[],"who_cares":["linux-kernel","kvm","amd-svm","nested-virtualization"],"confidence":0.3,"needs_auth":"unknown","worst_case":"unknown","analyst_note":"Find the upstream kernel fix commit and any CVSS score to confirm the impact and the affected kernel versions.","how_to_check":"- unknown","needs_analyst":true,"not_affected_if":["no-kvm-on-amd","no-nested-virtualization"],"who_is_affected":"Hosts running the Linux kernel with KVM on AMD SVM that run nested virtualization, where a hypervisor guest runs its own guests. Systems without KVM on AMD or without nested virtualization are unlikely to be affected, but the sources do not confirm this.","user_interaction":"unknown","needs_special_setup":"yes","severity_if_unknown":"unknown"},"cost_usd":0.00058,"input_tokens":3454,"output_tokens":470,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2026':12A,15A '-98716':13A,16A 'access':139C 'activ':61B,91C,109C,125C 'address':158C,176C 'alway':60B,117C 'amd':18B,35B 'amd-svm':17B 'anoth':180C 'assum':54B,113C 'attack':69B 'bitmap':7A,44B,56B,95C,106C,121C,161C 'bother':154C 'cach':173C 'cheap':169C 'check':4A,97C 'consult':39B 'cve':11A,14A 'descript':63B 'exploit':76B 'follow':82C 'gain':70B 'guest':10A,48B 'host':37B 'i.e':140C 'inform':185C 'instead':111C 'intercept':101C,137C 'introduc':178C 'kernel':23B,30B,80C 'kvm':2A,20B,32B,87C,115C,127C,145C 'l1':134C 'l2':49B,123C 'linux':1A,22B,29B,79C 'linux-kernel':21B 'merg':148C 'mismatch':74B 'modul':33B 'msprm01':149C 'msr':6A,42B,94C,99C,104C,138C 'msrpm02':129C 'msrpm12':151C 'need':146C 'nest':9A,25B,47B 'nested-virtu':24B 'permiss':43B,105C 'potenti':183C 'resolv':86C 'run':51B 'runtim':27B 'sourc':181C 'stale':184C 'state':66B 'svm':3A,19B,36B,88C 'track':155C 'use':89C,102C,118C,128C,165C 'va':167C 'virtual':26B,157C,175C 'vmcb':92C,110C 'vmcb02':58B,119C 'vulner':83C 'want':135C 'would':177C 'wrong':5A,41B 'x86':171C 'yet':179C","nicknames":[],"mitigations":[],"who_affected":"Hosts running the Linux kernel with KVM on AMD SVM that run nested virtualization, where a hypervisor guest runs its own guests. Systems without KVM on AMD or without nested virtualization are unlikely to be affected, but the sources do not confirm this.","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-2026-98716","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98716","severity":null,"published_at":"2026-10-18T16:17:25+00:00","modified_at":"2026-10-21T13:21:39+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"}