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Advisory severityHigh7.0Vendor: MediumRed Hat Linux

High [CVE-2026-63802] fix UAF in __blkcg_rstat_flush

This high-severity Red Hat Linux advisory covers CVE-2026-63802 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support, Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On.

Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.

CVE-2026-63802 Source published Source updated

VulniPulse record published Record updated

CVE-2026-63802
Affected products & platforms
Red Hat LinuxLinux Kernel
Open source advisory

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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 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 flaw was found in the Linux kernel's block input/output control group (blk-cgroup) component.

A race condition allows one group to remove another's entries while it is still in use, leading to premature memory deallocation. This can result in system instability or a denial of service.

Red Hat severity: Moderate — CVSS 7 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H). Weakness: CWE-825.

Affected products named by the advisory: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support; Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On; Red Hat Enterprise Linux 8.8 Telecommunications Update Service; and 5 more.

Affected versions

No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.

Official advisory · high-confidence parse· fetched 7 days ago·verify at source

Fixed versions
  • kernel-0:6.12.0-211.59.1.el10_2
  • kernel-rt-0:4.18.0-553.163.1.rt7.504.el8_10
  • kernel-0:4.18.0-553.163.1.el8_10
  • kernel-0:4.18.0-372.221.1.el8_6
  • kernel-0:4.18.0-477.175.1.el8_8
  • kernel-0:5.14.0-687.51.1.el9_8
  • kernel-0:5.14.0-427.158.1.el9_4
  • kernel-0:5.14.0-570.152.1.el9_6
  • RHSA-2026:71233
  • RHSA-2026:67469
  • RHSA-2026:67468
  • RHSA-2026:79783
  • RHSA-2026:84793
  • RHSA-2026:71232
  • RHSA-2026:91489
  • RHSA-2026:91492

Official advisory · high-confidence parse· fetched 7 days ago·verify at source

Mitigation

Upgrade to a fixed release: kernel-0:6.12.0-211.59.1.el10_2, kernel-rt-0:4.18.0-553.163.1.rt7.504.el8_10, kernel-0:4.18.0-553.163.1.el8_10, kernel-0:4.18.0-372.221.1.el8_6, kernel-0:4.18.0-477.175.1.el8_8, kernel-0:5.14.0-687.51.1.el9_8. That is the remediation for this advisory.

The vendor advisory may list interim mitigations or workarounds not captured here. Review it before change work.

Official advisory · high-confidence parse· fetched 7 days ago·verify at source

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