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CVE Record

CVE-2026-23375: mm: thp: deny THP for files on anonymous inodes

In the Linux kernel, the following vulnerability has been resolved: mm: thp: deny THP for files on anonymous inodes file_thp_enabled() incorrectly allows THP for files on anonymous inodes (e.g. guest_memfd and secretmem). These files are created via alloc_file_pseudo(), which does not call get_write_access() and leaves inode->i_writecount at 0. Combined with S_ISREG(inode->i_mode) being true, they appear as read-only regular files when CONFIG_READ_ONLY_THP_FOR_FS is enabled, making them eligible for THP collapse. Anonymous inodes can never pass the inode_is_open_for_write() check since their i_writecount is never incremented through the normal VFS open path. The right thing to do is to exclude them from THP eligibility altogether, since CONFIG_READ_ONLY_THP_FOR_FS was designed for real filesystem files (e.g. shared libraries), not for pseudo-filesystem inodes. For guest_memfd, this allows khugepaged and MADV_COLLAPSE to create large folios in the page cache via the collapse path, but the guest_memfd fault handler does not support large folios. This triggers WARN_ON_ONCE(folio_test_large(folio)) in kvm_gmem_fault_user_mapping(). For secretmem, collapse_file() tries to copy page contents through the direct map, but secretmem pages are removed from the direct map. This can result in a kernel crash: BUG: unable to handle page fault for address: ffff88810284d000 RIP: 0010:memcpy_orig+0x16/0x130 Call Trace: collapse_file hpage_collapse_scan_file madvise_collapse Secretmem is not affected by the crash on upstream as the memory failure recovery handles the failed copy gracefully, but it still triggers confusing false memory failure reports: Memory failure: 0x106d96f: recovery action for clean unevictable LRU page: Recovered Check IS_ANON_FILE(inode) in file_thp_enabled() to deny THP for all anonymous inode files.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This Linux kernel flaw can let normal memory optimization paths mishandle special anonymous inode files. In some configurations, that can cause warnings, false memory-failure reports, or a kernel crash. The issue appears configuration- and feature-dependent, not a broadly confirmed internet-facing exposure.

Executive priority

Treat this as a targeted kernel stability risk, especially for virtualization or sensitive-memory workloads. It should be patched through normal kernel maintenance, with higher priority where affected features are in use. Current sources do not justify emergency response for all Linux assets.

Technical view

file_thp_enabled() incorrectly permits THP collapse for anonymous inode files when CONFIG_READ_ONLY_THP_FOR_FS is enabled. guest_memfd can receive unsupported large folios, triggering a KVM warning. secretmem collapse can copy through the direct map although pages are removed from it, with crash behavior described in the CVE text.

Likely exposure

Exposure is most relevant to Linux systems using affected kernel versions with CONFIG_READ_ONLY_THP_FOR_FS enabled and workloads involving guest_memfd or secretmem. The bundle lists Linux affected versions including 6.8, 6.12.78, 6.18.17, 6.19.7, and 7.0, but exact distro impact needs vendor confirmation.

Exploitation context

The source bundle does not report active exploitation, and KEV status is false. The described impact comes from THP collapse behavior through khugepaged or MADV_COLLAPSE, but the bundle does not provide evidence of weaponized exploitation or privilege escalation.

Researcher notes

The fix direction is explicit: deny THP for IS_ANON_FILE(inode) inside file_thp_enabled(). Evidence supports availability and diagnostic-noise impacts, but not active exploitation, privilege escalation, or remote reachability. Upstream notes secretmem crash behavior differs because recovery handles the failed copy gracefully.

Mitigation direction

  • Apply Linux vendor kernel updates that include the referenced stable fixes.
  • Prioritize hosts running KVM workloads using guest_memfd or secretmem-sensitive workloads.
  • Check vendor advisories for exact affected distro kernels and backport status.
  • Do not assume a runtime workaround unless documented by the kernel or distro vendor.

Validation and detection

  • Inventory kernel versions and compare against vendor advisories for CVE-2026-23375.
  • Check whether CONFIG_READ_ONLY_THP_FOR_FS is enabled on relevant kernels.
  • Identify systems using KVM guest_memfd or secretmem features.
  • Review kernel logs for WARN_ON_ONCE, collapse_file, or memory failure messages matching the CVE description.
Prepared
Confidence
high
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
5Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

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  2. CVE publishedCVE Program

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  3. CVE updatedCVE Program

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Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux7fbb5e188248c50f737720825da1864ce42536d1, 7fbb5e188248c50f737720825da1864ce42536d1, 7fbb5e188248c50f737720825da1864ce42536d1, 7fbb5e188248c50f737720825da1864ce42536d1unaffected
LinuxLinux6.8, 0, 6.12.78, 6.18.17, 6.19.7, 7.0affected
Weakness

CWE details

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