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CVE Record

CVE-2026-23147: btrfs: zlib: fix the folio leak on S390 hardware acceleration

In the Linux kernel, the following vulnerability has been resolved: btrfs: zlib: fix the folio leak on S390 hardware acceleration [BUG] After commit aa60fe12b4f4 ("btrfs: zlib: refactor S390x HW acceleration buffer preparation"), we no longer release the folio of the page cache of folio returned by btrfs_compress_filemap_get_folio() for S390 hardware acceleration path. [CAUSE] Before that commit, we call kumap_local() and folio_put() after handling each folio. Although the timing is not ideal (it release previous folio at the beginning of the loop, and rely on some extra cleanup out of the loop), it at least handles the folio release correctly. Meanwhile the refactored code is easier to read, it lacks the call to release the filemap folio. [FIX] Add the missing folio_put() for copy_data_into_buffer().

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2026-23147 is a Linux kernel Btrfs compression bug affecting a specific S390x hardware-accelerated zlib path. A missing reference release can leak kernel memory objects over time. The public record does not provide CVSS scoring or evidence of active exploitation.

Executive priority

Treat as a targeted kernel maintenance issue, not an internet-wide emergency. Prioritize affected S390x Linux platforms using Btrfs compression, especially production systems where resource leaks could affect availability.

Technical view

After Linux commit aa60fe12b4f4 refactored Btrfs S390x zlib buffer preparation, the code stopped releasing a filemap folio returned by btrfs_compress_filemap_get_folio(). The fix adds the missing folio_put() in copy_data_into_buffer().

Likely exposure

Most relevant to Linux systems on S390x using Btrfs zlib compression with the affected kernel code. The source lists affected kernel ranges including 6.15, 6.18.9, and 6.19, but version metadata should be verified against vendor backports.

Exploitation context

No CISA KEV listing or cited source indicates active exploitation. The issue appears tied to a specific kernel compression execution path and may cause resource leakage rather than immediate code execution, based on provided sources.

Researcher notes

The public description is clear on root cause and fix but lacks CVSS, CWE, exploitability detail, and distribution-specific affected ranges. The affected version metadata appears limited; validate with downstream kernel maintainers before declaring exposure.

Mitigation direction

  • Check your Linux vendor advisory for CVE-2026-23147 and affected package versions.
  • Update to a kernel package that includes the referenced stable fixes.
  • Prioritize S390x systems using Btrfs with zlib compression for review.
  • If no vendor package exists, track the upstream stable commits for backport status.

Validation and detection

  • Inventory Linux S390x hosts and identify Btrfs usage.
  • Check whether Btrfs zlib compression is enabled on those systems.
  • Compare installed kernel versions against vendor guidance for this CVE.
  • Confirm kernel source or changelog includes the referenced stable fix commits.
  • Monitor for abnormal memory pressure only as a supporting signal, not proof.
Prepared
Confidence
medium
Sources
4

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

Conservative CVE-to-ATT&CK context

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CVE-2026-23147 mapping review

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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
3Source links

Vulnerability timeline

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

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxaa60fe12b4f49f49fc73e5023f8675e2df1f7805, aa60fe12b4f49f49fc73e5023f8675e2df1f7805unaffected
LinuxLinux6.15, 0, 6.18.9, 6.19affected
Weakness

CWE details

No CWE listed

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