{"id":"CVE-2026-89917","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: arm64: Handle VNCR TLB invalidation race with vcpu_put() VNCR unmapping\n\nWhile VNCR TLB invalidation always occurs under the MMU lock,\nvcpu_put() doesn't, while it…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: arm64: Handle VNCR TLB invalidation race with vcpu_put() VNCR unmapping\n\nWhile VNCR TLB invalidation always occurs under the MMU lock,\nvcpu_put() doesn't, while it…","severity":"medium","vendor":"Linux","product":"Linux","affected":["Linux >= 7270cc9157f474dfc46750a34c9d7defc686b2eb < 5cbd8761d001c11ada73b1753d772c4745a70e72","Linux >= 7270cc9157f474dfc46750a34c9d7defc686b2eb < 9065c1261f8a05c6a7a2d90048c7c0665ab2896d","Linux >= 7270cc9157f474dfc46750a34c9d7defc686b2eb < 38640bc32be3fcf9526d477155bc19d3f146231f","Linux 6.16"],"published":"2026-09-16","updated":"2026-09-16","sourceUpdated":"2026-09-16T11:17:00.763","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-89917","references":[{"url":"https://git.kernel.org/stable/c/38640bc32be3fcf9526d477155bc19d3f146231f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/5cbd8761d001c11ada73b1753d772c4745a70e72","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/9065c1261f8a05c6a7a2d90048c7c0665ab2896d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89917.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-89917"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2535260"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89917"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89917"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89917.mbox"},{"url":"https://kernelcve.org/list/?q=CVE-2026-89917"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"ingestedAt":"2026-09-16T10:53:53.973Z","epss":0.00206,"epssPercentile":0.10647,"cvss":4.7,"cvssVector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H","cvssSource":"vendor","cwe":["CWE-362"],"slug":"CVE-2026-89917","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nKVM: arm64: Handle VNCR TLB invalidation race with vcpu_put() VNCR unmapping\n\nWhile VNCR TLB invalidation always occurs under the MMU lock,\nvcpu_put() doesn't, while it unmaps the VNCR page.\n\nThe problem is that the invalidation evaluates vncr_tlb::cpu to\ndecide whether an unmapping needs to take place (cpu != -1) before\nperforming it. On the other hand, this_cpu_reset_vncr_fixmap()\nunconditionally unmaps if L1_VNCR_MAPPED is set.\n\nThese two obviously can race, with a TOCTOU pattern on the TLBI\npath, and a BUG_ON() on the vcpu_put() path. And the two can end-up\ncalling vncr_fixmap(-1), with extra lethal effects.\n\nMove the reset of vncr_tlb::cpu to -1 to a common function, and make\nthis update atomic so that only a single thread can reset the field\nand perform the corresponding unmap. The vcpu_put() still need to\nunconditionally unmap the current VNCR to close another ugly race.\n\nFinally, the assignment of vncr_tlb::cpu is moved to be kept in sync\nwith the actual mapping, similar to L1_VNCR_MAPPED being set.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10 · no fix planned: Red Hat Enterprise Linux 10 · updated 2026-10-24 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89917.json)","depth":"sunlit","depthScore":26,"depthScoreParts":{"impact":25.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":228554,"id":"CVE-2026-89917","ts":1792844784883,"field":"cvss","old":null,"new":"4.7"},{"seq":228553,"id":"CVE-2026-89917","ts":1792844784883,"field":"severity","old":"none","new":"medium"}]}