CVE-2026-64326

Task hang via unconditional block-device writeback

Published Jul 25, 2026 · Updated Jul 25, 2026

Denial of service in Linux Kernel 6.6 allows local users to hang kernel tasks by triggering surprise removal of a block device. On the bare block-device path without a mark_dead callback, bdev_mark_dead() calls sync_blockdev() even when surprise is true, waiting forever for writeback that cannot complete. Reachability requires a surprise-removal path with outstanding writeback; the hang wedges the reset worker and every task waiting on it.

CVSS severity5.5
Medium
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Linux Kernel 6.6 allows local users to hang kernel tasks by triggering surprise removal of a block device. On the bare block-device path without a mark_dead callback, bdev_mark_dead() calls sync_blockdev() even when surprise is true, waiting forever for writeback that cannot complete. Reachability requires a surprise-removal path with outstanding writeback; the hang wedges the reset worker and every task waiting on it.

The record

CVE
CVE-2026-64326
Published
Jul 25, 2026
Updated
Jul 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-390, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 25, 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=6.6
  2. Affected versionversion=d8530de5a6e82be0ce17a5fdf727a394bcf6444c <49f06cff50a4ccf3b7a1a662ceb892b3b21a527a
  3. Affected versionversion=d8530de5a6e82be0ce17a5fdf727a394bcf6444c <9818bcae3c0ca1dde4b9a334125c46676e0a9b29
  4. Affected versionversion=d8530de5a6e82be0ce17a5fdf727a394bcf6444c <aa4c4a9315764b2b7a7182e72cc5ea87520436b4
  5. Affected versionversion=d8530de5a6e82be0ce17a5fdf727a394bcf6444c <d6998ddd507c81e3829489a6ead23f17f5acb7fe
  6. Affected versionversion=d8530de5a6e82be0ce17a5fdf727a394bcf6444c <f41cf35ee2a1e31374b3f54e7579c55153506e70

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=6.6; version=d8530de5a6e82be0ce17a5fdf727a394bcf6444c <49f06cff50a4ccf3b7a1a662ceb892b3b21a527a; version=d8530de5a6e82be0ce17a5fdf727a394bcf6444c <9818bcae3c0ca1dde4b9a334125c46676e0a9b29; version=d8530de5a6e82be0ce17a5fdf727a394bcf6444c <aa4c4a9315764b2b7a7182e72cc5ea87520436b4; version=d8530de5a6e82be0ce17a5fdf727a394bcf6444c <d6998ddd507c81e3829489a6ead23f17f5acb7fe; version=d8530de5a6e82be0ce17a5fdf727a394bcf6444c <f41cf35ee2a1e31374b3f54e7579c55153506e70

Published CVSS scores

5.5Red HatCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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.

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

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-390Detection of Error Condition Without Action
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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