high
7.8
CWE
416
Advisory Published
Advisory Published
Updated

CVE-2023-31248: (Pwn2Own) Linux Kernel nftables Use-After-Free Local Privilege Escalation Vulnerability

First published: Wed Jul 05 2023(Updated: )

Last updated 25 April 2025

Credit: security@ubuntu.com security@ubuntu.com security@ubuntu.com

Affected SoftwareAffected VersionHow to fix
Red Hat Kernel-devel
Linux Kernel>=5.9<5.10.188
Linux Kernel>=5.11<5.15.121
Linux Kernel>=5.16<6.1.39
Linux Kernel>=6.2<6.4.4
Red Hat Fedora=37
Red Hat Fedora=38
Debian Linux=11.0
Ubuntu=14.04
Ubuntu=16.04
Ubuntu=18.04
Ubuntu=20.04
Ubuntu=22.04
Linux Kernel=5.9.0-rc1
debian/linux
5.10.223-1
5.10.234-1
6.1.129-1
6.1.135-1
6.12.25-1

Remedy

https://lore.kernel.org/netfilter-devel/20230705121627.GC19489@breakpoint.cc/T/

Remedy

If not needed, disable the ability for unprivileged users to create namespaces. To do this temporarily, do: sudo sysctl -w kernel.unprivileged_userns_clone=0 To disable across reboots, do: echo kernel.unprivileged_userns_clone=0 | \ sudo tee /etc/sysctl.d/99-disable-unpriv-userns.conf

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Reference Links

Frequently Asked Questions

  • What is the severity of CVE-2023-31248?

    CVE-2023-31248 is considered a high severity local privilege escalation vulnerability.

  • How do I fix CVE-2023-31248?

    To mitigate CVE-2023-31248, update to a patched version of the Linux kernel, such as 5.10.223-1 or 6.1.123-1.

  • Which versions of the Linux kernel are affected by CVE-2023-31248?

    CVE-2023-31248 impacts Linux kernel versions between 5.9 and 6.4.4, including specific distributions like Fedora and Ubuntu.

  • Can CVE-2023-31248 be exploited remotely?

    CVE-2023-31248 requires local access for exploitation, meaning an attacker must have local user capabilities.

  • What does the CVE-2023-31248 vulnerability involve?

    CVE-2023-31248 involves a use-after-free condition in the nftables subsystem of the Linux kernel that could lead to privilege escalation.

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