---
id: CVE-2026-63802
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  blk-cgroup: fix UAF in __blkcg_rstat_flush()

  When multiple blkgs in the same blkcg are released concurrently,
  a use-after-free can occur
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  blk-cgroup: fix UAF in __blkcg_rstat_flush()

  When multiple blkgs in the same blkcg are released concurrently,
  a use-after-free can occur. The race happens when one blk…
severity: high
published: '2026-07-19'
updated: '2026-07-19'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63802'
references:
  - url: 'https://git.kernel.org/stable/c/0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/5e5b7f2ef854936e95dceb6a2fdfefcb7152d2c6'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/96e545410c4f74c89d496c1d5d9ef8d08f14368b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/afebe44facc48a61761e885bbb7f0380d4a603ec'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/bbebd9425cad3573d1527441753899b926525a0f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63802.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-63802'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2502251'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-63802'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63802'
  - url: >-
      https://lore.kernel.org/linux-cve-announce/2026071901-CVE-2026-63802-1c53@gregkh/T
  - url: 'https://access.redhat.com/errata/RHSA-2026:67468'
  - url: 'https://access.redhat.com/errata/RHSA-2026:67469'
tags:
  - nvd
  - csaf
  - vex
  - red-hat
ingestedAt: '2026-07-20T01:35:22.919Z'
epss: 0.00132
epssPercentile: 0.03148
vendor: Red Hat
product: Red Hat Enterprise Linux 9
affected:
  - enterprise_linux 10
  - enterprise_linux 6
  - enterprise_linux 9
  - enterprise_linux_baseos_v_8
  - enterprise_linux_crb_v_8
  - enterprise_linux_nfv_v_8
  - enterprise_linux_rt_v_8
patched:
  - enterprise_linux_baseos_v_8
  - enterprise_linux_crb_v_8
  - enterprise_linux_nfv_v_8
  - enterprise_linux_rt_v_8
cvss: 7
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: vendor
cwe:
  - CWE-825
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

blk-cgroup: fix UAF in __blkcg_rstat_flush()

When multiple blkgs in the same blkcg are released concurrently,
a use-after-free can occur. The race happens when one blkg's
__blkcg_rstat_flush() removes another blkg's iostat entries via
llist_del_all(). The second blkg sees an empty list and proceeds
to free itself while the first is still iterating over its entries.

Move the flush from __blkg_release() (RCU callback) to blkg_release()
(before call_rcu). This ensures the RCU grace period waits for any
concurrent flush's rcu_read_lock() section to complete before freeing.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **RHSA-2026:67468** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS (v. 8), Red Hat Enterprise Linux CRB (v. 8) · released 2026-09-15 · [advisory](https://access.redhat.com/errata/RHSA-2026:67468)
- **RHSA-2026:67469** · Red Hat · fixed in: Red Hat Enterprise Linux NFV (v. 8), Red Hat Enterprise Linux RT (v. 8) · released 2026-09-15 · [advisory](https://access.redhat.com/errata/RHSA-2026:67469)
- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · updated 2026-09-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63802.json)