CVE-2022-34918

Published: 4 July 2022

An issue was discovered in the Linux kernel through 5.18.9. A type confusion bug in nft_set_elem_init (leading to a buffer overflow) could be used by a local attacker to escalate privileges, a different vulnerability than CVE-2022-32250. (The attacker can obtain root access, but must start with an unprivileged user namespace to obtain CAP_NET_ADMIN access.) This can be fixed in nft_setelem_parse_data in net/netfilter/nf_tables_api.c.

From the Ubuntu Security Team

Arthur Mongodin discovered that the netfilter subsystem in the Linux kernel did not properly perform data validation. A local attacker could use this to escalate privileges in certain situations.

Mitigation

Unprivileged user namespaces can be disabled via:
  sudo sysctl kernel.unprivileged_userns_clone=0
This will affect browser sandboxing, container runtimes, etc.
so may not be appropriate for all environments.

Status

Severity score breakdown

References

• https://www.openwall.com/lists/oss-security/2022/07/02/3
• https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=7e6bc1f6cabcd30aba0b11219d8e01b952eacbb6
• https://lore.kernel.org/netfilter-devel/cd9428b6-7ffb-dd22-d949-d86f4869f452@randorisec.fr/T/#u
• http://www.openwall.com/lists/oss-security/2022/07/05/1
• https://www.randorisec.fr/crack-linux-firewall/
• https://ubuntu.com/security/notices/USN-5540-1
• https://ubuntu.com/security/notices/USN-5544-1
• https://ubuntu.com/security/notices/USN-5545-1
• https://ubuntu.com/security/notices/USN-5560-1
• https://ubuntu.com/security/notices/USN-5560-2
• https://ubuntu.com/security/notices/USN-5562-1
• https://ubuntu.com/security/notices/USN-5564-1
• https://ubuntu.com/security/notices/USN-5566-1
• https://ubuntu.com/security/notices/USN-5582-1
• https://www.cve.org/CVERecord?id=CVE-2022-34918
• NVD
• Launchpad
• Debian