CVE-2026-93800Public exploitHinoki check available

Kernel crash via dangling Btrfs relocation root

Published Sep 24, 2026 · Updated Sep 24, 2026

Use-after-free in Linux Btrfs 6.12 before 6.12.111 and 6.18 before 6.18.53 allows local users to crash the kernel on unmount. When btrfs_update_reloc_root() fails, insert_dirty_subvol() omits the root from dirty_subvol_roots, so cleanup frees the relocation root without clearing root->reloc_root. Reaching the faulty path requires privileged Btrfs balance or relocation activity plus an I/O failure; btrfs_put_root() later uses the dangling pointer, causing a kernel crash or double-free attempt.

CVSS severityUnavailable
Unscored
EPSS probability0.17%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Use-after-free in Linux Btrfs 6.12 before 6.12.111 and 6.18 before 6.18.53 allows local users to crash the kernel on unmount. When btrfs_update_reloc_root() fails, insert_dirty_subvol() omits the root from dirty_subvol_roots, so cleanup frees the relocation root without clearing root->reloc_root. Reaching the faulty path requires privileged Btrfs balance or relocation activity plus an I/O failure; btrfs_put_root() later uses the dangling pointer, causing a kernel crash or double-free attempt.

The record

CVE
CVE-2026-93800
Published
Sep 24, 2026
Updated
Sep 24, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Sep 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 24, 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 <6.12.111
  2. Affected versionversion=0 <6.18.53
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <83201804efa4a5168be754e1dfc9b2faee760cac
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <97a540d72ebcb21853d11f2a56782fe377f358e7
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <fda1b6636ff1846f00643e791099db5564b547d9

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linuxversion=0 <6.12.111; version=0 <6.18.53; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <83201804efa4a5168be754e1dfc9b2faee760cac; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <97a540d72ebcb21853d11f2a56782fe377f358e7; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <fda1b6636ff1846f00643e791099db5564b547d9

Published CVSS scores

No CVSS assessment is available in this record.

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.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

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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