UBUNTU-CVE-2026-89916: Critical severity ubuntu/linux-hwe-edge vulnerability
In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Make VNCR invalidation participate in MMU invalidation retry A VNCR TLB invalidation can occur on one vcpu while another vcpu is faulting in this same page. Without correctly handling this, we can end up with the following scenario: - vcpu A walks the PTs to translate VNCR - before vcpu A is able to grab the MMU lock to insert the TLB, vcpu B updates the S1 PTs with an invalid entry, and issues a TLBI S1E2 for this VA - vcpu A inserts the TLB for something that is now invalid This isn't a new problem, and we manage S2 by having the MMU notifier to bump up mmuinvalidateseq on invalidation so that the fault can be replayed. We can perform something similar here, and extend invalidatevncrva() to update the same counter, clearly indicating that the context has changed under our feet. This is safe as the invalidation always happen while holding the MMU lock for write, and that we sample the sequence number before walking S1.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42~24.04.1 - Upgrade
Upgrade
ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1~24.04.1 - Upgrade
Upgrade
ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-42.42 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1016.17 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
Upgrade
ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1015.16 - Upgrade
Upgrade
ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1
Event History
Frequently Asked Questions
What systems are realistically exposed to this issue?
The flaw concerns KVM on arm64 and a race involving VNCR TLB invalidation while virtual CPUs access the same page. The listed affected Ubuntu kernel packages are linux-riscv, linux-realtime, linux-hwe-edge, linux-azure, linux-gcp, linux-azure-fde, linux-gke, and linux-aws-5.0.
What condition is required for the race to occur?
Two virtual CPUs must race on the same VNCR page: one CPU is walking page tables to translate VNCR, while another updates stage-1 page tables with an invalid entry and issues a S1E2 TLB invalidation for that virtual address. The first CPU can otherwise insert a TLB entry after that translation has become invalid.
What does the fix change?
The fix makes VNCR invalidation update the MMU invalidation sequence counter. A fault that observed an older sequence can then be replayed instead of installing a stale translation.