CVE-2026-80590

A flaw was found in the Linux kernel's network fragment reassembly process. An unprivileged local user, or a guest in a virtualized environment, could craft specially formed IPv4 or IPv6 network fragments that incorrectly retain Generic Segmentation Offload (GSO) state after reassembly. This misinterpretation of network packet state can lead to a kernel panic, resulting in a Denial of Service (DoS) for the affected system.

This vulnerability is rated as Important because local unprivileged actors or virtual machine guests can induce a kernel panic, leading to a complete host denial of service. In Red Hat Enterprise Linux deployments, untrusted network packets with attached segmentation offload descriptors can traverse the defragmentation pipeline via virtual interfaces or user namespaces. Because packet reassembly fails to strip these offload flags, subsequent core networking operations fail assertion checks in interrupt context. The capability of low-privileged tenants to crash the host operating system justifies the Important rating.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, restrict the creation of unprivileged user namespaces. This can prevent unprivileged local users from exploiting the vulnerability via tap devices. To disable unprivileged user namespaces, set the kernel.unprivileged_userns_clone sysctl to 0: sysctl -w kernel.unprivileged_userns_clone=0 To make this change persistent across reboots, add the following line to a file in /etc/sysctl.d/, for example, /etc/sysctl.d/99-disable-userns.conf: kernel.unprivileged_userns_clone = 0 After modifying the sysctl configuration, apply the changes: sysctl --system Disabling unprivileged user namespaces may impact applications that rely on this feature, such as container runtimes or sandboxing tools.