CVE-2026-63954

Host crash via uninitialized HPFS buffer release

Published Jul 19, 2026 · Updated Jul 19, 2026

Memory corruption in the Linux Kernel HPFS component allows local users to crash the host through a crafted filesystem image. When hpfs_map_dnode_bitmap fails during a directory operation, the HPFS allocation path calls hpfs_brelse4 on an uninitialized quad_buffer_head, releasing stack-garbage pointers. Triggering the flaw requires mounting the image and write access to the mountpoint; CAP_SYS_ADMIN inside an unprivileged user namespace is sufficient, and the result is a kernel oops or panic.

CVSS severity7.8
High
EPSS probability0.17%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in the Linux Kernel HPFS component allows local users to crash the host through a crafted filesystem image. When hpfs_map_dnode_bitmap fails during a directory operation, the HPFS allocation path calls hpfs_brelse4 on an uninitialized quad_buffer_head, releasing stack-garbage pointers. Triggering the flaw requires mounting the image and write access to the mountpoint; CAP_SYS_ADMIN inside an unprivileged user namespace is sufficient, and the result is a kernel oops or panic.

The record

CVE
CVE-2026-63954
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-824, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <5.10.259
  2. Affected versionversion=0 <5.15.210
  3. Affected versionversion=0 <6.1.176
  4. Affected versionversion=0 <6.12.93
  5. Affected versionversion=0 <6.18.35
  6. Affected versionversion=0 <6.6.143
  7. Affected versionversion=0 <7.0.12
  8. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <010b08084000ef018f1a8de5197087f3b91d8cfe
  9. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <0886c6f257fe3663f80218aa1919b0f3f21bf22c
  10. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1648a3c7f4e18f46a4881920133fc4f2494185a0
  11. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1d73a533760bc5abb83b3cc759133596f7bb708f
  12. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <4f37bb30b57d6d403d02673074555bd3c3602bef
  13. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <7c58c55a2a16f7274772507bd1637be609351b4f
  14. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <974820a59efde7c1a7e1260bcfe9bb81f833cc9f
  15. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <d98d8562b3284b5a5c8eb67e71b794508e46e288

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=0 <5.10.259; version=0 <5.15.210; version=0 <6.1.176; version=0 <6.12.93; version=0 <6.18.35; version=0 <6.6.143; version=0 <7.0.12; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <010b08084000ef018f1a8de5197087f3b91d8cfe; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <0886c6f257fe3663f80218aa1919b0f3f21bf22c; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1648a3c7f4e18f46a4881920133fc4f2494185a0; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1d73a533760bc5abb83b3cc759133596f7bb708f; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <4f37bb30b57d6d403d02673074555bd3c3602bef; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <7c58c55a2a16f7274772507bd1637be609351b4f; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <974820a59efde7c1a7e1260bcfe9bb81f833cc9f; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <d98d8562b3284b5a5c8eb67e71b794508e46e288

Published CVSS scores

7.8kernel.orgCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 11, 2026Sep 17, 2026
Latest reporting daySep 17, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-824Access of Uninitialized Pointer
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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