Improper update of reference count in Linux kernel - CVE-2026-53026

Vulnerability identifier: #VU135347

CSH Severity: Medium

CVSS v4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-53026

CWE-ID: CWE-911

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote user to cause a denial of service.

The vulnerability exists due to improper reference count management in nfsd4_add_rdaccess_to_wrdeleg when handling concurrent NFS file access state updates. A remote user can trigger concurrent access patterns to cause a denial of service.

The issue can leave nfsd_file objects unreleased and trigger a BUG in kmem_cache_destroy() when the nfs-server service is stopped.

Linux kernel
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for ARM 64
Ubuntu
kernel (Red Hat package)
linux (Ubuntu package)
linux-ibm (Ubuntu package)
linux-aws (Ubuntu package)
linux-oem-7.0 (Ubuntu package)
linux-azure (Ubuntu package)
linux-gcp-7.0 (Ubuntu package)
linux-oracle-7.0 (Ubuntu package)
linux-azure-7.0 (Ubuntu package)
linux-nvidia (Ubuntu package)
linux-nvidia-bos (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
kernel (Red Hat package) - update to 6.12.0-211.50.1.el10_2
linux (Ubuntu package) - addressed in versions 7.0.0-28.28, 7.0.0-28.28.1, 7.0.0-1003.4, 7.0.0-1008.8
linux-ibm (Ubuntu package) - addressed in versions 7.0.0-1008.8, 7.0.0-1010.10
linux-aws (Ubuntu package) - addressed in versions 7.0.0-1009.9, 7.0.0-1015.15
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1009.9
linux-azure (Ubuntu package) - addressed in versions 7.0.0-1009.9, 7.0.0-1010.10
linux-gcp-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-oracle-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-azure-7.0 (Ubuntu package) - update to 7.0.0-1014.14~24.04.1
linux-nvidia (Ubuntu package) - addressed in versions 7.0.0-1016.16, 7.0.0-1016.16~24.04.1
linux-nvidia-bos (Ubuntu package) - update to 7.0.0-2016.16

• https://git.kernel.org/stable/c/4584229395d0d65bd517780afe97ffea07cb2c3d
• https://git.kernel.org/stable/c/b48f44f36e6607b2f818560f19deb86b4a9c717b
• https://git.kernel.org/stable/c/b81572b073441dfd32213e41857676d0dbff4665

• Improper update of reference count in Linux kernel nfsd
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux
• Ubuntu update for linux-ibm
• Ubuntu update for linux-azure
• Ubuntu update for linux-aws
• Ubuntu update for linux-nvidia-bos
• Ubuntu update for linux-nvidia
• Red Hat Enterprise Linux 10 update for kernel
• Ubuntu update for linux-gcp-7.0
• Ubuntu update for linux-oracle-7.0
• Ubuntu update for linux-azure-7.0