CVE-2026-63802 Details
Description
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.
A use-after-free vulnerability has been identified in the Linux kernel's block cgroup management. This issue arises when multiple block cgroup groups (blkgs) within the same block cgroup (blkcg) are released simultaneously. The vulnerability occurs because one blkg's flush operation can inadvertently remove another blkg's I/O statistics entries, leading the second blkg to incorrectly perceive an empty list and free itself while the first blkg is still processing its entries. This flaw has been addressed by changing the timing of the flush operation, ensuring that the necessary synchronization is in place before freeing resources.
Users can upgrade to the latest version of the Linux kernel where this vulnerability has been fixed. Instructions for downloading the patched version can be found on the official Linux kernel website.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
No SSVC data is available for this CVE.
References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://git.kernel.org/stable/c/0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2 | kernel.org | Patch |
| https://git.kernel.org/stable/c/5e5b7f2ef854936e95dceb6a2fdfefcb7152d2c6 | kernel.org | Patch |
| https://git.kernel.org/stable/c/96e545410c4f74c89d496c1d5d9ef8d08f14368b | kernel.org | Patch |
| https://git.kernel.org/stable/c/afebe44facc48a61761e885bbb7f0380d4a603ec | kernel.org | Patch |
| https://git.kernel.org/stable/c/bbebd9425cad3573d1527441753899b926525a0f | kernel.org | Patch |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-416 | Use After Free | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| linux linux kernel | >= 6.3.9, < 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 - 6.4 rc7 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Aug 17, 2026 | CVE Modified | kernel.org |
| Jul 29, 2026 | Initial Analysis | [email protected] |
| Jul 20, 2026 | CVE Modified | kernel.org |
| Jul 19, 2026 | New CVE Received | kernel.org |