CVE-2026-63802

High

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.

Package Linux Kernel
Published 2026-07-19
Last modified 2026-08-17
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

7.8

out of 10
High
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness type

CWE-416

CVE-2026-63802 is a Use After Free vulnerability

What is Use After Free?

The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. Learn more on MITRE CWE

Affected versions

Linux kernel versions 6.3.9, 6.4 and later are affected. Fixed in 6.6.144, 6.12.95, 6.18.38, 7.1.3, 7.2 and their respective stable series.

Affected from
≥ 6.3.9 ≥ 6.4
Fixed in
✓ 6.6.144 6.6.x ✓ 6.12.95 6.12.x ✓ 6.18.38 6.18.x ✓ 7.1.3 7.1.x ✓ 7.2

References

5 total

Frequently asked questions

  • What is CVE-2026-63802?

    CVE-2026-63802 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10 , classified as an Use After Free flaw (CWE-416) . It affects Linux kernel versions from 6.3.9 onward and has been patched in 6.6.144, 6.12.95, 6.18.38 and others. CVE-2026-63802 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2026-63802?

    CVE-2026-63802 has a CVSS score of 7.8 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H .

  • Is there a patch available for CVE-2026-63802?

    Yes. CVE-2026-63802 has been patched. Fixed versions include 6.6.144, 6.12.95, 6.18.38 and others. If you are running Linux kernel 6.3.9 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2026-63802 actively exploited?

    No. CVE-2026-63802 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

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