medium CVSS 5.5

CVE-2026-98164·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: KVM: x86/mmu: Check write tracking in all address spaces kvm_gfn_is_write_tracked() checks only the supplied memslot, but page tracking is per-address-space and shadow pages are shared across all address spaces. With SMM, a GFN can therefore be write-tracked in one address space and appear untracked through the other. Check the supplied slot first, then the slot for the other address space. This ensures all callers honor write tracking regardless of the active address space. In particular, it prevents mmu_try_to_unsync_pages() from marking an upper-level shadow page unsync and eventually triggering the BUG in pte_list_remove(). [invert direction of the conditional. - Paolo]

Severity
medium
Software
Kernel
Fixed in
7.1.13
Published
2026-09-29

Affected versions

From: 6.19

Until: 7.1.13

Fixed in: 7.1.13

How to fix this CVE

Update your Linux kernel to version 7.1.13 or later to resolve a memory management unit (MMU) tracking inconsistency that could cause system instability. This patch ensures write-tracking metadata is properly checked across all KVM address spaces, preventing unsynchronized shadow page table corruption. Apply the update through your distribution's package manager at your earliest convenience.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Run `uname -r` to display your current kernel version and compare against the affected range 6.19–7.1.12.
  2. Check if KVM virtualization is enabled with `kvm-ok` (Ubuntu/Debian) or `grep -c 'vmx\|svm' /proc/cpuinfo` to confirm the vulnerable code path is present.
  3. Search kernel logs for KVM-related errors with `dmesg | grep -i 'kvm\|mmu\|pte_list' | tail -20` to identify any shadow page table corruption events.
  4. After patching, verify the new kernel is running with `uname -r` and ensure it displays 7.1.13 or later.

FAQ

What is CVE-2026-98164?

This is a Linux kernel vulnerability in KVM's memory management unit (MMU) that fails to consistently check write-tracking metadata across different address spaces used in System Management Mode (SMM). This inconsistency can allow shadow page tables to become unsynchronized and trigger kernel crashes.

Is CVE-2026-98164 being actively exploited?

No, there is no evidence of active exploitation in the wild, and no public exploits are available for this vulnerability.

What versions of Kernel are affected by CVE-2026-98164?

Linux kernel versions 6.19 through 7.1.12 are affected. Version 7.1.13 and later contain the fix.

How do I check if my server is vulnerable to CVE-2026-98164?

Run `uname -r` and compare the output against 6.19–7.1.12. If your kernel falls within this range, your system is vulnerable and requires an update.

Does Defensia detect CVE-2026-98164?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2026-98164 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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CVE-2026-43501CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ipv6: rpl: reserve mac_len headroom when recompressed SRH grows ipv6_rpl_srh_rcv() decompresses an RFC 6554 Source Routing Header, swaps the next segment into ipv6_hdr->daddr, recompresses, then pulls the old header and pushes the new one plus the IPv6 header back. The recompressed header can be larger than the received one when the swap reduces the common-prefix length the segments share with daddr (CmprI=0, CmprE>0, seg[0][0] != daddr[0] gives the maximum +8 bytes). pskb_expand_head() was gated on segments_left == 0, so on earlier segments the push consumed unchecked headroom. Once skb_push() leaves fewer than skb->mac_len bytes in front of data, skb_mac_header_rebuild()'s call to: skb_set_mac_header(skb, -skb->mac_len); will store (data - head) - mac_len into the u16 mac_header field, which wraps to ~65530, and the following memmove() writes mac_len bytes ~64KiB past skb->head. A single AF_INET6/SOCK_RAW/IPV6_HDRINCL packet over lo with a two segment type-3 SRH (CmprI=0, CmprE=15) reaches headroom 8 after one pass; KASAN reports a 14-byte OOB write in ipv6_rthdr_rcv. Fix this by expanding the head whenever the remaining room is less than the push size plus mac_len, and request that much extra so the rebuilt MAC header fits afterwards.
CVE-2026-64216CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: netfs: Fix potential UAF in netfs_unlock_abandoned_read_pages() netfs_unlock_abandoned_read_pages(rreq) accesses the index of the folios it is wanting to unlock and compares that to rreq->no_unlock_folio so that it doesn't unlock a folio being read for netfs_perform_write() or netfs_write_begin(). However, given that netfs_unlock_abandoned_read_pages() is called _after_ NETFS_RREQ_IN_PROGRESS is cleared, the one folio that it's not allowed to dereference is the one specified by ->no_unlock_folio as ownership immediately reverts to the caller. Fix this by storing the folio pointer instead and using that rather than the index. Also fix netfs_unlock_read_folio() where the same applies.

References

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