--- 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' - url: 'https://access.redhat.com/errata/RHSA-2026:71233' - url: 'https://access.redhat.com/errata/RHSA-2026:71232' - url: 'https://access.redhat.com/errata/RHSA-2026:79783' - url: 'https://access.redhat.com/errata/RHSA-2026:84793' tags: - nvd - csaf - vex - red-hat - cve.org ingestedAt: '2026-07-20T01:35:22.919Z' epss: 0.00102 epssPercentile: 0.00934 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 ssvc: exploitation: none automatable: 'no' technicalImpact: total timestamp: '2026-10-16T15:30:46.711290Z' scores: vendor: 7 cna: 7.8 --- ## 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 6, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 9 · updated 2026-10-19 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63802.json) - **RHSA-2026:71233** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10), Red Hat Enterprise Linux Real Time for NFV (v. 10), Red Hat Enterprise Linux Real Time (v. 10) · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71233) - **RHSA-2026:71232** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Real Time for NFV (v. 9), Red Hat Enterprise Linux Real Time (v. 9) · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71232) - **RHSA-2026:79783** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS AUS (v.8.6), Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.6) · released 2026-10-09 · [advisory](https://access.redhat.com/errata/RHSA-2026:79783) - **RHSA-2026:84793** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS E4S (v.8.8), Red Hat Enterprise Linux BaseOS TUS (v.8.8) · released 2026-10-19 · [advisory](https://access.redhat.com/errata/RHSA-2026:84793)