Use-after-free in Linux kernel - CVE-2026-63804
Published: July 21, 2026
Vulnerability identifier: #VU138844
CSH Severity: Low
CVSS v4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-63804
CWE-ID: CWE-416
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local user to cause a denial of service.
The vulnerability exists due to a use-after-free in gfs2_qd_dealloc when processing pending RCU callbacks during filesystem unmount. A local user can trigger quota object disposal and unmount-related cleanup to cause a denial of service.
The issue occurs because an RCU callback may access the superblock after it has already been freed.
Affected software
Linux kernel
How to mitigate CVE-2026-63804
Install security update from vendor's repository.
Linux kernel - update to 7.0 rc3
External References
- https://git.kernel.org/stable/c/4fe388218826df8607ae41a6305df67db08a9093
- https://git.kernel.org/stable/c/8745d9f7e1682c39f0a1578895ac74205e2a6757
- https://git.kernel.org/stable/c/9d0d5ba20cad661f7f287d4c66d2c19022ce2fd0
- https://git.kernel.org/stable/c/b85ef03f726b15047a6fa6d11b639bdf6c0ee4f0
- https://git.kernel.org/stable/c/f9c9ec2c319f843b70ecdf939d48b52d189bc081