(Pwn2Own) Linux Kernel nftables Use-After-Free Local Privilege Escalation Vulnerability

July 6th, 2023
ZDI-23-899 ZDI-CAN-20717

CVE ID

CVE-2023-31248

CVSS Score

7.8 AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected Vendors

Linux

Affected Products

Kernel

Vulnerability Details

This vulnerability allows local attackers to escalate privileges on affected installations of Linux Kernel. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability.

The specific flaw exists within the handling of nft_chains. The issue results from the lack of validating the status of a chain while processing lookup on the chain. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of the kernel.

Additional Details

Linux has issued an update to correct this vulnerability. More details can be found at:
https://lore.kernel.org/netfilter-devel/20230705121627.GC19489@breakpoint.cc/T/

Disclosure Timeline

  • 2023-05-09 - Vulnerability reported to vendor
  • 2023-07-06 - Coordinated public release of advisory

Credit

Mingi Cho of Theori

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