# CVE-2026-64181 — Linux

> As of 2026-07-20, CVE-2026-64181 is a HIGH-severity vulnerability in Linux, CVSS v3.1 7.8, EPSS 0.1% (5.7th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-64181 as of 2026-07-20; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-07-20

## What is CVE-2026-64181?

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.

Its CVSS v3 base vector states that the flaw requires local access to the host, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 78 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.8 — HIGH (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **EPSS (FIRST):** 0.1% probability of exploitation in the next 30 days, higher than 5.7% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 4.1/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-07-19, last modified 2026-07-20

## Is CVE-2026-64181 being exploited?

It currently carries a trending score of 31 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [Linux](https://intel.threadlinqs.com/vendors/linux): Linux

## How to fix CVE-2026-64181

No vendor patch reference has been recorded for CVE-2026-64181 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-64181

No threat campaign in the Threadlinqs corpus currently references CVE-2026-64181, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-07-21. This product uses the NVD API but is not endorsed or certified by the NVD.

**Other references**

- [git.kernel.org](https://git.kernel.org/stable/c/62153767e8fc3889bc6508e9ffe927aaf64c4334)
- [git.kernel.org (9052ea2ee2233be5d4786b8909151ca2bfbedf99)](https://git.kernel.org/stable/c/9052ea2ee2233be5d4786b8909151ca2bfbedf99)
- [git.kernel.org (c0c6ccd9828c3a1950623b546fa57292a77b5c73)](https://git.kernel.org/stable/c/c0c6ccd9828c3a1950623b546fa57292a77b5c73)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-64181
Full detection coverage and IOCs for threats exploiting CVE-2026-64181 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp