A security update for the Linux kernel in Red Hat Enterprise Linux 6 Extended Lifecycle Support addresses a vulnerability identified as CVE-2026-99999. The issue involves improper validation of the checksum_start value in the IPv4 implementation. Red Hat has released patches to fix this vulnerability and recommends applying the update and rebooting the system to ensure protection. The update is rated as Important by Red Hat Product Security.

Red Hat Security Advisory: kernel security update

The kernel packages contain the Linux kernel, the core of any Linux operating system.

Security Fix(es):

* kernel: ipv4: validate checksum_start before completing checksum (CVE-2026-99999)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

The kernel-rt packages provide the Real Time Linux Kernel, which enables fine-tuning for systems with extremely high determinism requirements.

Security Fix(es):

* kernel: ipv4: validate checksum_start before completing checksum (CVE-2026-99999)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Red Hat Security Advisory: kernel-rt security update

The kernel packages contain the Linux kernel, the core of any Linux operating system.

Security Fix(es):

* kernel: ipv4: validate checksum_start before completing checksum (CVE-2026-99999)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Additional Changes:

For detailed information on changes in this release, see the NVIDIA for RHEL 10 Release Notes linked from the References section.

kernel

A security vulnerability in the Linux kernel's IPv4 implementation was identified and fixed by Red Hat. The issue involves improper validation of the checksum_start parameter before completing the checksum calculation. This vulnerability is tracked as CVE-2026-99999 and affects Red Hat Enterprise Linux 9.4 versions. Red Hat has released a security update to address this issue and recommends applying the update and rebooting the system to ensure the fix takes effect.

linux

An issue in the Linux kernel's virtio-net/TAP networking path affects KVM-based hypervisors running unpatched Linux kernel versions 4.4 through 6.18. This vulnerability allows an attacker with privileged access inside a guest virtual machine to send specially crafted network packets that can corrupt host kernel memory, potentially leading to host memory disclosure or denial of service. AWS-managed compute and container services are not affected, and no action is required for customers using these services.

Issue in the Linux kernel virtio-net/TAP networking path affecting KVM-based hypervisors

linux-aws

linux-azure

linux-lts-xenial

linux-aws-hwe

linux-gcp

linux-hwe

linux-hwe-edge

linux-kvm

linux-oracle

linux-fips

linux-aws-5.0

linux-aws-5.3

linux-aws-5.4

linux-azure-4.15

linux-azure-5.3

linux-azure-5.4

linux-azure-edge

linux-gcp-4.15

linux-gcp-5.3

linux-gcp-5.4

linux-gke-4.15

linux-gke-5.4

linux-gkeop-5.4

linux-hwe-5.4

linux-ibm-5.4

linux-oem

linux-oracle-5.0

linux-oracle-5.3

linux-oracle-5.4

linux-raspi-5.4

linux-aws-fips

linux-azure-fips

linux-gcp-fips

linux-aws-5.11

linux-aws-5.13

linux-aws-5.15

linux-aws-5.8

linux-azure-5.11

linux-azure-5.13

linux-azure-5.15

linux-azure-5.8

linux-azure-fde

linux-azure-fde-5.15

linux-bluefield

linux-gcp-5.11

linux-gcp-5.13

linux-gcp-5.15

linux-gcp-5.8

linux-gke

linux-gke-5.15

linux-gkeop

linux-gkeop-5.15

linux-hwe-5.11

linux-hwe-5.13

linux-hwe-5.15

linux-hwe-5.8

linux-ibm

linux-ibm-5.15

linux-intel-5.13

linux-intel-iotg-5.15

linux-iot

linux-lowlatency-hwe-5.15

linux-nvidia-tegra-5.15

linux-oem-5.10

linux-oem-5.13

linux-oem-5.14

linux-oem-5.6

linux-oracle-5.11

linux-oracle-5.13

linux-oracle-5.15

linux-oracle-5.8

linux-raspi

linux-raspi2

linux-riscv

linux-riscv-5.11

linux-riscv-5.15

A critical vulnerability in the Linux kernel IPv4 stack allows malformed packets with bad checksum metadata to cause corruption of the network header. This can lead to severe impacts including confidentiality, integrity, and availability violations. The issue arises because the checksum_start value was not validated before completing the checksum calculation, allowing skb_checksum_help to corrupt packet data. A fix has been implemented to validate checksum_start before checksum completion as a defense-in-depth measure.

CVE-2026-99999: ipv4: validate checksum_start before completing checksum in Linux kernel

A critical vulnerability in the Linux kernel IPv4 stack allows packets with bad checksum metadata to cause corruption of the network header via skb_checksum_help. This flaw was discovered by Paulos and independently reproduced by others. The issue arises from insufficient validation of checksum_start before completing the checksum calculation. A fix has been implemented to add this validation as a defense-in-depth measure, with more comprehensive input validation planned for the future.

Search: CVE-2026-99999