Use-after-free in Linux kernel - CVE-2026-89990

Vulnerability identifier: #VU150291

CSH Severity: High

CVSS v4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-89990

CWE-ID: CWE-416

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to execute arbitrary code.

The vulnerability exists due to use-after-free in ceph_mds_check_access() when a concurrent MDS session reopen occurs while access is being checked. A remote attacker can trigger concurrent access checking and MDS session reopening to execute arbitrary code.

Linux kernel
Debian Linux
Ubuntu
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-gcp (Ubuntu package)
linux-oracle (Ubuntu package)
linux-ibm (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)
linux (Debian package)

Install security update from vendor's repository.

linux (Ubuntu package) - update to 7.0.0-42.42
linux-aws (Ubuntu package) - update to 7.0.0-1016.17
linux-gcp (Ubuntu package) - update to 7.0.0-1016.18
linux-oracle (Ubuntu package) - update to 7.0.0-1015.16
linux-ibm (Ubuntu package) - update to 7.0.0-1017.17
linux-hwe-7.0 (Ubuntu package) - update to 7.0.0-42.42~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1017.17
linux (Debian package) - update to 6.12.111-1

• https://git.kernel.org/stable/c/729c1ff670ece6f3d4b1738365a0b2f90d487523
• https://git.kernel.org/stable/c/a61c6ae1dae2611082b831b4aaa780878099c012
• https://git.kernel.org/stable/c/ca5bfea2045ef2eb3305cf2a9d8da549b76c37d3
• https://git.kernel.org/stable/c/df1a97d5313fccadb08390306d49b194fb027392

• Use-after-free in Linux kernel ceph
• Debian update for linux
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux, linux-aws, linux-gcp and more