Canonical released today new Linux kernel versions for all supported Ubuntu operating system releases to address a regression introduced by the latest kernel security update.

Last week, Canonical released Linux kernel updates for all supported Ubuntu releases to address several security vulnerabilities discovered by Jonathan Looney in Linux kernel's TCP retransmission queue implementation when handling some specific TCP Selective Acknowledgment (SACKs).

Known as SACK Panic, these security vulnerabilities affect Ubuntu 19.04, Ubuntu 18.10, Ubuntu 18.04 LTS, and Ubuntu 16.04 LTS systems and could allow a remote attacker to crash the affected systems by causing a denial of service by constructing an ongoing sequence of requests.

However, it would appear that the Linux kernel patch pushed by Canonical in the main software repositories of all supported Ubuntu Linux releases introduced a regression that interfered with certain networking apps with very low SO_SNDBUF values. Therefore, they now released new kernel versions.

"USN-4017-1 fixed vulnerabilities in the Linux kernel for Ubuntu. Unfortunately, the update introduced a regression that interfered with networking applications that setup very low SO_SNDBUF values. This update fixes the problem. We apologize for the inconvenience," reads the new security advisory.

Users are urged to updated their installations

Canonical urges all Ubuntu users to update their installations to the new Linux kernel versions available in the official software repositories for all supported architectures and platforms, including 32-bit, 64-bit, Raspberry Pi 2, OEM processors, cloud environments, and Snapdragon processors.

The new Linux kernel versions are linux-image-5.0.0-20.21 for Ubuntu 19.04, linux-image-4.18.0-25.26 for Ubuntu 18.10, linux-image-4.15.0-54.58 for Ubuntu 18.04 LTS, linux-image-4.15.0-54.58~16.04.1 for Ubuntu 16.04 LTS, and linux-image-4.4.0-154.181~14.04.1 for Ubuntu 14.04 ESM. Please reboot your systems after installing the new kernel versions.