CVE-2026-98469: KVM: arm64: Fix AArch32 DBGBXVR<n> handling
In the Linux kernel, the following vulnerability has been resolved:
KVM: arm64: Fix AArch32 DBGBXVR<n> handling
The consolidation of the breakpoint and watchpoint register accessors switched DBGBXVR<n> from trapbvr() to trapdbgwbreg(). The latter selects backing storage with demuxwbreg(), which only handles Op2 values 4 through 7. Since DBGBXVR<n> uses Op2 1, an AArch32 guest access hits KVMBUGON() and marks the VM dead.
DBGBXVR<n> aliases DBGBVR<n>EL1[63:32], and its AA32(HI) descriptor already selects the upper half. Map Op2 1 to dbgbvr[] alongside Op2 4, restoring the pre-regression behavior.
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
Upgrade
ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1016.17 - Upgrade
Upgrade
ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
Upgrade
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
Upgrade
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
Who is exposed to this issue?
KVM deployments on arm64 that run AArch32 guests are exposed when those guests access the DBGBXVR<n> debug register. The described outcome is that KVM marks the affected VM dead.
What must an attacker or guest do to trigger the failure?
An AArch32 guest must access DBGBXVR<n>, which uses Op2 value 1. That access reaches a KVM_BUG_ON() because the affected register demultiplexing path only handles Op2 values 4 through 7.
What is the mitigation if an update cannot be applied immediately?
The provided information supports avoiding AArch32 guest access to DBGBXVR<n>. No configuration-based mitigation or workaround is specified.
How can I determine whether a VM was affected?
The described symptom is that KVM marks the VM dead after an AArch32 guest accesses DBGBXVR<n>. The provided information does not specify a log message or other detection indicator.