CVE-2024-1085

Published: 31 January 2024

A use-after-free vulnerability in the Linux kernel's netfilter: nf_tables component can be exploited to achieve local privilege escalation. The nft_setelem_catchall_deactivate() function checks whether the catch-all set element is active in the current generation instead of the next generation before freeing it, but only flags it inactive in the next generation, making it possible to free the element multiple times, leading to a double free vulnerability. We recommend upgrading past commit b1db244ffd041a49ecc9618e8feb6b5c1afcdaa7.

From the Ubuntu Security Team

Lonial Con discovered that the netfilter subsystem in the Linux kernel did not properly handle element deactivation in certain cases, leading to a use-after-free vulnerability. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code.

Notes

Priority reason:
By passing a certain filter value to nf_tables, an unprivileged local attacker can elevate privileges.

from Google kCTF.

Mitigation

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

Status

Severity score breakdown

References

• https://kernel.dance/b1db244ffd041a49ecc9618e8feb6b5c1afcdaa7
• https://git.kernel.org/linus/b1db244ffd041a49ecc9618e8feb6b5c1afcdaa7 (6.8-rc1)
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b1db244ffd041a49ecc9618e8feb6b5c1afcdaa7
• https://ubuntu.com/security/notices/USN-6688-1
• https://ubuntu.com/security/notices/USN-6704-1
• https://ubuntu.com/security/notices/USN-6705-1
• https://ubuntu.com/security/notices/USN-6707-1
• https://ubuntu.com/security/notices/USN-6704-2
• https://ubuntu.com/security/notices/USN-6707-2
• https://ubuntu.com/security/notices/USN-6704-3
• https://ubuntu.com/security/notices/USN-6707-3
• https://ubuntu.com/security/notices/USN-6704-4
• https://ubuntu.com/security/notices/USN-6707-4
• https://www.cve.org/CVERecord?id=CVE-2024-1085
• NVD
• Launchpad
• Debian

Bugs

• https://bugzilla.redhat.com/show_bug.cgi?id=2262127
• https://bugzilla.suse.com/show_bug.cgi?id=1219429