CVE-2026-74663

A flaw was found in the Linux kernel. An attacker could create overly deep queueing discipline (qdisc) hierarchies, leading to excessive recursion in qdisc tree walkers. This can exhaust the kernel stack, resulting in a Denial of Service (DoS) due to a system crash.

A low impact flaw was found in the Linux kernel's traffic control (net/sched) subsystem. A local attacker with the ability to configure queueing disciplines (qdisc), which requires the CAP_NET_ADMIN capability, could create overly deep qdisc hierarchies through the create-and-graft path, which was not covered by the existing loop check. Such deep hierarchies cause excessive recursion in qdisc tree walkers and can exhaust the kernel stack, resulting in a kernel crash and denial of service. Only availability is affected; there is no impact on confidentiality or integrity.

Red Hat Enterprise Linux 7, 8, 9, and 10 (kernel and kernel-rt) and Red Hat In-Vehicle OS 2 (kernel and kernel-ivos-qualcomm) are affected. The fix is deferred for these streams because the flaw is rated low impact and requires local privileged access, so it will be addressed in a future scheduled kernel update; the residual risk is that a local attacker able to configure traffic control could panic the kernel and crash the system. The Red Hat Enterprise Linux 6 kernel is out of support and no fix is planned for that stream.

The Red Hat severity for this flaw is low impact, with a CVSS3 score of 5.5 (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H), while the upstream CVE record assigns a score of 7.8 (IMPORTANT) that includes high confidentiality and integrity impacts. That difference exists because the technical evidence supports only a denial of service through kernel stack exhaustion, with no confidentiality or integrity impact.

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.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.