kernel: kernel: Incorrect TLB flushing in RISC-V KVM via improper nested acceleration update order (CVE-2026-98639)

Overview

A flaw was found in the Linux kernel's KVM (Kernel-based Virtual Machine) subsystem for the RISC-V architecture. During nested virtualization acceleration, control flags are written before the target page parameters are properly committed to shared memory. Consequently, the supervisor interface or underlying hardware can process outdated parameters, resulting in incorrect flushes of the Translation Lookaside Buffer (TLB, a cache used to speed up memory address translation). A local user or guest virtual machine could exploit this behavior to cause memory corruption, expose stale memory data, or induce a denial of service (DoS).

Vendor advisories

• Red Hat VEX · Important · affected: Red Hat Enterprise Linux 10 · no fix planned: Red Hat Enterprise Linux 10 · updated 2026-10-21 · vex

kernel: kernel: Incorrect TLB flushing in RISC-V KVM via improper nested acceleration update order — rated Important by Red Hat. Released 2026-10-18, updated 2026-10-21.

Affected:

• Red Hat Enterprise Linux 10

No fix planned:

• Red Hat Enterprise Linux 10

Remediation

Fix deferred

Workarounds / mitigations:

• Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.