Red Hat Product Security released an advisory (RHSA-2026:24381) for a kernel security update addressing three vulnerabilities in Red Hat Enterprise Linux 9 kernel packages. CVE-2026-31613 fixes an out-of-bounds read vulnerability in the SMB client when parsing symlink error responses. CVE-2026-31786 addresses a buffer overflow in the Xen hypervisor driver (drivers/xen/sys-hypervisor.c). CVE-2026-46243 mitigates acceptance of userspace cifs.spnego descriptions by the SMB client. The advisory classifies the update as important and recommends applying the update and rebooting the system. A CVSS score is not provided in the advisory, but the severity is indicated as important. The update affects multiple architectures and variants of Red Hat Enterprise Linux 9 and CodeReady Linux Builder 9. The vendor advisory provides detailed package information and instructions for applying the update.

The vulnerabilities could lead to out-of-bounds memory reads and buffer overflows in kernel components related to SMB client functionality and Xen hypervisor drivers. These issues may allow attackers to cause denial of service or potentially execute arbitrary code within the kernel context. The acceptance of malicious userspace cifs.spnego descriptions could also lead to unexpected behavior or security bypasses in SMB client authentication. Red Hat rates the security impact as important, indicating a high risk to affected systems if unpatched.

Red Hat has released an official security update that fixes these vulnerabilities. Users of Red Hat Enterprise Linux 9 and related products should apply the kernel update provided in advisory RHSA-2026:24381 as soon as possible. The update requires a system reboot to take effect. Detailed instructions and updated packages are available at https://access.redhat.com/articles/11258. No alternative mitigations are indicated; applying the official patch is required to remediate these issues.