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Review reviewHigh

CVE-2026-63802

Linux Linux, linux kernel

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_r...

CVSS
7.8
EPSS
-
- percentile
CISA KEV
Not listed
Published
2026.07.19
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability-
Technical severityCVSS 7.8

Vulnerability 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_r...

Affected product and versions

Product
Linux Linux, linux kernel
Affected versions
>= 20cb1c2fb7568a6054c55defe044311397e01ddb < 96e545410c4f74c89d496c1d5d9ef8d08f14368b, >= 20cb1c2fb7568a6054c55defe044311397e01ddb < bbebd9425cad3573d1527441753899b926525a0f, >= 20cb1c2fb7568a6054c55defe044311397e01ddb < 5e5b7f2ef854936e95dceb6a2fdfefcb7152d2c6, >= 20cb1c2fb7568a6054c55defe044311397e01ddb < afebe44facc48a61761e885bbb7f0380d4a603ec, >= 20cb1c2fb7568a6054c55defe044311397e01ddb < 0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2, >= 0f6090d90f627d8c58f939067d6c6821ce1b3c68, >= 6.3.9 < 6.4, >= 6.4, >= 6.4.1 < 6.6.144, >= 6.7 < 6.12.95, >= 6.13 < 6.18.38, >= 6.19 < 7.1.3, 6.4
Fixed versions
6.4, 6.6.144, 6.12.95, 6.18.38, 7.1.3

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Linux Linux, linux kernel and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
CWE-416