Vulnerability in Linux kernel (CVE-2026-64181)
Summary
Vulnerability in Linux kernel (CVE-2026-64181). Successful exploitation can lead to full system takeover.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
mm: fix __vm_normal_page() to handle missing support for pmd_special()/pud_special()
On x86 32-bit with THP enabled, zap_huge_pmd() is seen to generate a
"WARNING: mm/memory.c:735 at __vm_normal_page+0x6a/0x7d", from the
VM_WARN_ON_ONCE(is_zero_pfn(pfn) || is_huge_zero_pfn(pfn)); followed by
"BUG: Bad rss-counter state"s, then later "BUG: Bad page state"s when
reclaim gets to call shrink_huge_zero_folio_scan().
It's as if the _PAGE_SPECIAL bit never got set in the huge_zero pmd: and
indeed, whereas pte_special() and pte_mkspecial() are subject to a
dedicated CONFIG_ARCH_HAS_PTE_SPECIAL, pmd_special() and pmd_mkspecial()
are subject to CONFIG_ARCH_SUPPORTS_PMD_PFNMAP, which is never enabled on
any 32-bit architecture.
While the problem was exposed through commit d80a9cb1a64a
("mm/huge_memory: add and use normal_or_softleaf_folio_pmd()"), it was an
oversight in commit af38538801c6 ("mm/memory: factor out common code from
vm_normal_page_*()") and would result in other problems:
- huge zero folio accounted in smaps, pagemap (PAGE_IS_FILE) and
numamaps as file-backed THP - folio_walk_start() returning the folio even without FW_ZEROPAGE set.
Callers seem to tolerate that, though.
... and triggering the VM_WARN_ON_ONE(), although never reported so far.
To fix it, teach vm_normal_page_pmd()/vm_normal_page_pud() to consider
whether pmd_special/pud_special is actually implemented.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-64181 has been found in Linux kernel.
Successful exploitation can lead to full system takeover. CVSS score: 7.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-64181" on the vendor's site.
CVE-2026-64181 (Linux kernel) — CVSS v3 7.8
Attack vector: local / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (unclassified) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: High (CVSS 7.8/10). Successful exploitation can lead to full system takeover.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- BellSoft Alpaquita BELL-CVE-2026-64181 linux-lts Fixed in: 6.18.35-r1
- Debian DEBIAN-CVE-2026-64181 linux Fixed in: 7.0.12-1
- Ubuntu UBUNTU-CVE-2026-64181 linux-hwe-edge
References
- advisory nvd.nist.gov
- advisory github.com
- package git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web github.com