# CVE-2026-98464: RISC-V: KVM: Synchronize hrtimer callback during teardown

CVE-2026-98464 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-98464, released October 19, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-98464
- Priority: High
- CVSS: 9.3 (Moderate)
- EPSS: 0.0014
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 18, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-98464

## Description

In the Linux kernel, the following vulnerability has been resolved:  RISC-V: KVM: Synchronize hrtimer callback during teardown  The non-Sstc hrtimer callback clears next_set before its final uses of the enclosing vCPU.  If teardown observes next_set as false while the callback is still running, kvm_riscv_vcpu_timer_cancel() skips hrtimer_cancel() and kvm_destroy_vcpus() can free the vCPU before the callback enters kvm_riscv_vcpu_set_interrupt().  A guest can arm the timer with SBI TIME and request shutdown with SBI legacy shutdown or SRST.  A VMM that honors KVM_EXIT_SYSTEM_EVENT and destroys the VM supplies the teardown side of the race; no post-launch host ioctl is needed to arm or request teardown.  On upstream master 62cc90241548, generic KASAN reported:    BUG: KASAN: slab-use-after-free in do_raw_spin_lock   Write of size 4 at addr ff60000005e58898    kvm_riscv_vcpu_set_interrupt   kvm_riscv_vcpu_hrtimer_expired   __hrtimer_run_queues   hrtimer_interrupt  The object was allocated by KVM_CREATE_VCPU and freed concurrently by:    kvm_destroy_vcpus   kvm_arch_destroy_vm   kvm_destroy_vm   __fput  For deterministic validation, I added mdelay(1000) immediately after the existing next_set = false assignment.  This only widens the existing post-clear callback window.  A no-delay trace build naturally reached the callback-after-teardown-start/before-deinit ordering in 12 of 200 runs, but 1,500 stock-kernel stress iterations did not produce a KASAN report, so natural reproduction is timing-sensitive.  Always invoke hrtimer_cancel() for an initialized timer.  Preserve the existing -EINVAL result when the timer is no longer set, but only after synchronizing with a running callback.  With this patch, hrtimer_cancel() blocked for the full widened callback window before vCPU destruction.  KASAN reported no error in 100 fixed-and-widened runs or 200 fix-only timing-sweep runs.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.190-1 | [DEBIAN-CVE-2026-98464](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98464.md) | Oct 19, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.113-1 | [DEBIAN-CVE-2026-98464](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98464.md) | Oct 19, 2026 |
| Linux | linux Debian 14 | 7.2.9-1 | [DEBIAN-CVE-2026-98464](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98464.md) | Oct 19, 2026 |
| Linux | linux-6.12 Debian 12.15 (bookworm) | 6.12.113-1~deb12u1 | [DEBIAN-CVE-2026-98464](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98464.md) | Oct 19, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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