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CVE-2026-89915— KVM: arm64: Remove VM-wide VNCR mapping counter

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Linux 内核中，以下漏洞已得到修复： KVM: arm64: 移除全局 VNCR 映射计数器 该全局 VNCR 映射计数器用于在处理 TLB 失效时，判断 L1 提供的 VNCR 页面是否在任意 CPU 上映射到 L0。当在固定映射（fixmap）中建立映射时，计数器递增；当取消映射时，计数器递减。 事实证明，这种跟踪机制存在几个缺陷： 我们本意是使 TLB 失效，而该映射只是 TLB 操作的一个附带结果。使用此计数器来判断是否需要使 TLB 失效，可能会导致遗漏某些应执行的失效操作。 当 L1 vCPU

CVSS 9.3 · Critical EPSS 0.18% · P8

Possible ATT&CK Techniques 1 AI

T1069 · Permission Groups Discovery

Affected Version Matrix 8

VendorProduct Version RangeStatus
Linux Linux 4ffa72ad8f37e73bbb6c0baa88557bcb4fd39929< 5453b85c7ebb605febac3df42021f9471663f051 affected
4ffa72ad8f37e73bbb6c0baa88557bcb4fd39929< 87c2bbf189829dce4aaada8f82e3d54ccc037976 affected
4ffa72ad8f37e73bbb6c0baa88557bcb4fd39929< c55bc773b6e814406658fae7dc5c15f639ed816e affected
6.16 affected
< 6.16 unaffected
6.18.52≤ 6.18.* unaffected
7.2.5≤ 7.2.* unaffected
7.3-rc1≤ * unaffected
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I. Basic Information for CVE-2026-89915

Vulnerability Information
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Vulnerability Title
KVM: arm64: Remove VM-wide VNCR mapping counter
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Remove VM-wide VNCR mapping counter The global VNCR mapping counter is used to decide whether an L1 provided VNCR page is mapped in L0 on any CPU at the point of dealing with a TLB invalidation. It is incremented when a mapping is made in the fixmap, and decremented when unmapped. As it turns out, this tracking has several flaws: - we are trying to invalidate TLBs, and the mapping is only an opportunistic consequence of the TLB. Checking this counter to decide whether a TLB needs to be invalidated may result in missed invalidations. - an L1 vcpu invalidating its own TLB (a very likely case) will not succeed in invalidating the VNCR pseudo TLB because that page is not mapped in L0 at this stage. Given that this tracking fails at delivering the minimum guarantees that are required and is only a performance optimisation, remove it completely.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 4ffa72ad8f37e73bbb6c0baa88557bcb4fd39929 ~ 5453b85c7ebb605febac3df42021f9471663f051 -
Linux Linux 6.16 -

II. Public POCs for CVE-2026-89915

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III. Intelligence Information for CVE-2026-89915

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Other References for CVE-2026-89915 (3)

Same Patch Batch · Linux · 2026-09-16 · 276 CVEs total

CVE-2026-90048 9.8 CRITICAL fs/ntfs3: fix slab-out-of-bounds write in ni_create_attr_list()
CVE-2026-90012 9.8 CRITICAL spi: Fix DMA mapping ownership on partial map failure
CVE-2026-89970 9.8 CRITICAL nvmet-auth: Synchronize timeout work during SQ teardown
CVE-2026-89857 9.8 CRITICAL scsi: qla2xxx: Hold qpair lock when sending NVMe LS reject
CVE-2026-89969 9.8 CRITICAL nvmet-tcp: fix out-of-bounds write when receiving an over-long PDU
CVE-2026-89847 9.8 CRITICAL scsi: qla2xxx: Avoid double completion in async IOCB timeout
CVE-2026-89972 9.8 CRITICAL nvme: add missing SRCU grace period in error path
CVE-2026-89990 9.8 CRITICAL ceph: lock mutex in ceph_mds_check_access()
CVE-2026-90036 9.8 CRITICAL NFSD: Prevent client use-after-free during blocked-lock reaping
CVE-2026-90038 9.8 CRITICAL NFSD: Prevent client use-after-free during export state revocation
CVE-2026-90037 9.8 CRITICAL NFSD: Prevent client use-after-free during close_lru reaping
CVE-2026-90042 9.8 CRITICAL ceph: properly decrypt filenames in vmalloc() buffers
CVE-2026-89778 9.8 CRITICAL isofs: fix out-of-bounds page array access on empty zisofs block
CVE-2026-89788 9.8 CRITICAL ksmbd: fix tree connection use-after-free in smb2_tree_connect()
CVE-2026-89783 9.8 CRITICAL xfrm6: fix out-of-bounds write in xfrm6_input_addr() when secpath is full
CVE-2026-89914 9.3 CRITICAL KVM: arm64: Sign-extend VA for range-based TLBI invalidation
CVE-2026-89930 9.3 CRITICAL KVM: nVMX: Service local TLB flushes on failed nested VM-Enter
CVE-2026-89918 9.3 CRITICAL KVM: arm64: Correctly handle end of VA space TLBI invalidation
CVE-2026-89916 9.3 CRITICAL KVM: arm64: Make VNCR invalidation participate in MMU invalidation retry
CVE-2026-90049 9.3 CRITICAL net: skbuff: don't skb_tx_error() the source skb in skb_zerocopy()

Showing top 20 of 276 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-89915

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