CVE-2026-98639
In the Linux kernel, the following vulnerability has been resolved: KVM: riscv: Fix NACL hfence entry update order The SBI v3.0 specification (section 15.1.2) requires a nested HFENCE entry to be populated as follows: 1) find an unused entry with Config.Pending == 0 2) update the Page_Number and Page_Count words 3) update the Config word with Config.Pending set __kvm_riscv_nacl_hfence() writes the Config word first, so the SBI implementation (or NACL hardware) can observe a pending entry with pnum/pcount values left over from the previous use of that entry, resulting in incorrect TLB flush ranges. Write pnum and pcount first and the Config word last. Since the consumer is an external agent on coherent shared memory, use WRITE_ONCE() to stop the compiler from reordering the stores and smp_wmb() to make the parameter words globally visible before the Pending bit is set.
Affected versions
Linux kernel versions
6.13
and later are affected. Fixed in
6.18.55,
7.2.9,
7.3
and their respective stable series.
References
3 totalFrequently asked questions
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What is CVE-2026-98639?
CVE-2026-98639 is a unscored severity Linux kernel vulnerability . It affects Linux kernel versions from 6.13 onward and has been patched in 6.18.55, 7.2.9 and 7.3. CVE-2026-98639 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
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Is there a patch available for CVE-2026-98639?
Yes. CVE-2026-98639 has been patched. Fixed versions include 6.18.55, 7.2.9 and 7.3. If you are running Linux kernel 6.13 or later up to the fix versions, apply the relevant patch for your kernel branch.
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Is CVE-2026-98639 actively exploited?
No. CVE-2026-98639 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.