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[USN-8616-1] Linux kernel (IBM) vulnerabilities

Posted on 29 July 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8616-1
July 28, 2026

linux-ibm, linux-ibm-5.4 vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux-ibm: Linux kernel for IBM cloud systems
- linux-ibm-5.4: Linux kernel for IBM cloud systems

Details:

It was discovered that the Linux kernel did not properly handle shared page
fragments during socket buffer operations, collectively known as Dirty
Frag. A logic flaw existed in the XFRM ESP-in-TCP subsystem and in the
RxRPC networking subsystem when processing paged fragments. A local
attacker could use this to escalate privileges, or possibly escape a
container. (CVE-2026-43284, CVE-2026-43500)

It was discovered that a logic flaw existed in the XFRM ESP-in-TCP
subsystem in the Linux kernel when handling socket buffer fragments. This
flaw is known as Fragnesia. A local attacker could use this to escalate
privileges, or possibly escape a container. (CVE-2026-43503)

Several security issues were discovered in the Linux kernel.
An attacker could possibly use these to compromise the system.
This update corrects flaws in the following subsystems:
- InfiniBand drivers;
- STMicroelectronics network drivers;
- NVME drivers;
- SCSI subsystem;
- USB over IP driver;
- Network file system (NFS) server daemon;
- SMB network file system;
- Tracing infrastructure;
- B.A.T.M.A.N. meshing protocol;
- Ethernet bridge;
- Ceph Core library;
- IPv4 networking;
- IPv6 networking;
- Netfilter;
- RDS protocol;
- RxRPC session sockets;
- X.25 network layer;
(CVE-2026-23272, CVE-2026-23455, CVE-2026-31402, CVE-2026-31418,
CVE-2026-31607, CVE-2026-31637, CVE-2026-31649, CVE-2026-31659,
CVE-2026-31682, CVE-2026-31685, CVE-2026-43011, CVE-2026-43037,
CVE-2026-43038, CVE-2026-43117, CVE-2026-43383, CVE-2026-43407,
CVE-2026-43414, CVE-2026-43494, CVE-2026-45988, CVE-2026-46043,
CVE-2026-46119, CVE-2026-46135, CVE-2026-46243)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 20.04 LTS
linux-image-5.4.0-1107-ibm 5.4.0-1107.112
Available with Ubuntu Pro
linux-image-ibm-5.4 5.4.0.1107.136
Available with Ubuntu Pro
linux-image-ibm-lts-20.04 5.4.0.1107.136
Available with Ubuntu Pro

Ubuntu 18.04 LTS
linux-image-5.4.0-1107-ibm 5.4.0-1107.112~18.04.1
Available with Ubuntu Pro
linux-image-ibm 5.4.0.1107.112~18.04.1
Available with Ubuntu Pro
linux-image-ibm-5.4 5.4.0.1107.112~18.04.1
Available with Ubuntu Pro

After a standard system update you need to reboot your computer to make
all the necessary changes.

ATTENTION: Due to an unavoidable ABI change the kernel updates have
been given a new version number, which requires you to recompile and
reinstall all third party kernel modules you might have installed.
Unless you manually uninstalled the standard kernel metapackages
(e.g. linux-generic, linux-generic-lts-RELEASE, linux-virtual,
linux-powerpc), a standard system upgrade will automatically perform
this as well.

References:
https://ubuntu.com/security/notices/USN-8616-1
CVE-2026-23272, CVE-2026-23455, CVE-2026-31402, CVE-2026-31418,
CVE-2026-31607, CVE-2026-31637, CVE-2026-31649, CVE-2026-31659,
CVE-2026-31682, CVE-2026-31685, CVE-2026-43011, CVE-2026-43037,
CVE-2026-43038, CVE-2026-43117, CVE-2026-43284, CVE-2026-43383,
CVE-2026-43407, CVE-2026-43414, CVE-2026-43494, CVE-2026-43500,
CVE-2026-43503, CVE-2026-45988, CVE-2026-46043, CVE-2026-46119,
CVE-2026-46135, CVE-2026-46243


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