CVE-2026-63802

Local memory corruption via blk-cgroup flush race

Published Jul 19, 2026 · Updated Jul 19, 2026

Use-after-free in Linux Kernel 6.3.9 through 6.4 and later affected branches allows local users to corrupt kernel memory. The __blkcg_rstat_flush() function calls llist_del_all() on a peer blkg's iostat list, letting that peer observe an empty list and free itself while the first flush still iterates its entries. Low-privileged local access and concurrent blkg teardown are required; successful triggering leaves the flush dereferencing freed kernel objects.

CVSS severity7.8
High
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Linux Kernel 6.3.9 through 6.4 and later affected branches allows local users to corrupt kernel memory. The __blkcg_rstat_flush() function calls llist_del_all() on a peer blkg's iostat list, letting that peer observe an empty list and free itself while the first flush still iterates its entries. Low-privileged local access and concurrent blkg teardown are required; successful triggering leaves the flush dereferencing freed kernel objects.

The record

CVE
CVE-2026-63802
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-416
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=0f6090d90f627d8c58f939067d6c6821ce1b3c68
  2. Affected versionversion=20cb1c2fb7568a6054c55defe044311397e01ddb <0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2
  3. Affected versionversion=20cb1c2fb7568a6054c55defe044311397e01ddb <5e5b7f2ef854936e95dceb6a2fdfefcb7152d2c6
  4. Affected versionversion=20cb1c2fb7568a6054c55defe044311397e01ddb <96e545410c4f74c89d496c1d5d9ef8d08f14368b
  5. Affected versionversion=20cb1c2fb7568a6054c55defe044311397e01ddb <afebe44facc48a61761e885bbb7f0380d4a603ec
  6. Affected versionversion=20cb1c2fb7568a6054c55defe044311397e01ddb <bbebd9425cad3573d1527441753899b926525a0f
  7. Affected versionversion=6.3.9 <6.4
  8. Affected versionversion=6.4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=0f6090d90f627d8c58f939067d6c6821ce1b3c68; version=20cb1c2fb7568a6054c55defe044311397e01ddb <0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2; version=20cb1c2fb7568a6054c55defe044311397e01ddb <5e5b7f2ef854936e95dceb6a2fdfefcb7152d2c6; version=20cb1c2fb7568a6054c55defe044311397e01ddb <96e545410c4f74c89d496c1d5d9ef8d08f14368b; version=20cb1c2fb7568a6054c55defe044311397e01ddb <afebe44facc48a61761e885bbb7f0380d4a603ec; version=20cb1c2fb7568a6054c55defe044311397e01ddb <bbebd9425cad3573d1527441753899b926525a0f; version=6.3.9 <6.4; version=6.4

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

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free

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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