Improper access control in Linux kernel - CVE-2026-31717

Vulnerability identifier: #VU128984

CSH Severity: Low

CVSS v4: 2.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-31717

CWE-ID: CWE-284

Exploitation vector: Remote access

Exploit availability: Public exploit is available

The vulnerability allows a remote user to hijack an orphaned durable handle.

The vulnerability exists due to improper access control in durable handle reconnect validation in ksmbd when processing SMB2 durable handle reconnect requests. A remote user can predict or brute-force the persistent ID and reconnect to the orphaned handle to hijack an orphaned durable handle.

The issue occurs because the reconnecting user's security context is not verified against the original opener's identity.

Linux kernel
Debian Linux
openEuler
Ubuntu
python3-perf-debuginfo
kernel
bpftool
bpftool-debuginfo
kernel-debuginfo
kernel-debugsource
kernel-devel
kernel-headers
kernel-source
kernel-tools
kernel-tools-debuginfo
kernel-tools-devel
perf
perf-debuginfo
python3-perf
kernel-extra-modules
linux (Debian package)
linux (Ubuntu package)
linux-azure (Ubuntu package)
linux-nvidia (Ubuntu package)
linux-raspi (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
python3-perf-debuginfo - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
kernel - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
bpftool - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
bpftool-debuginfo - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
kernel-debuginfo - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
kernel-debugsource - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
kernel-devel - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
kernel-headers - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
kernel-source - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
kernel-tools - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
kernel-tools-debuginfo - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
kernel-tools-devel - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
perf - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
perf-debuginfo - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
python3-perf - addressed in versions 6.6.0-145.1.19.156, 6.6.0-145.3.17.150
kernel-extra-modules - update to 6.6.0-145.3.17.150
linux (Debian package) - update to 6.12.94-1
linux (Ubuntu package) - update to 7.0.0-27.27
linux-azure (Ubuntu package) - addressed in versions 7.0.0-1009.9, 7.0.0-1010.10
linux-nvidia (Ubuntu package) - update to 7.0.0-1013.13
linux-raspi (Ubuntu package) - update to 7.0.0-1014.14

• Exploit #12703 - CVE-2026-31717-KSMBD-Exploit () (May 15, 2026)

• https://git.kernel.org/stable/c/00ce8d6789dae72d042a4522264964c72891ca37
• https://git.kernel.org/stable/c/49110a8ce654bbe56bef7c5e44cce31f4b102b8a
• https://git.kernel.org/stable/c/c908c853f304a4969b5aa10eba0b50350cc65b80

• Improper access control in Linux kernel smb server
• Debian update for linux
• Ubuntu update for linux
• Ubuntu update for linux-raspi
• openEuler 24.03 LTS SP3 update for kernel
• Ubuntu update for linux-nvidia
• Ubuntu update for linux-azure
• openEuler 24.03 LTS SP1 update for kernel