CVE-2026-74663 net/sched: reject overly deep qdisc hierarchies
Attackers can cause kernel stack exhaustion and denial of service by creating excessively deep qdisc hierarchies in the Linux kernel.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74663?
CVE-2026-74663 is a high-severity denial of service vulnerability in Linux, published on 22 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net/sched: reject overly deep qdisc hierarchies
Deep qdisc hierarchies can lead to excessive recursion in qdisc tree walkers and exhaust the kernel stack. The existing loop check does not cover the create-and-graft path, so a hierarchy can still be extended by creating a new child qdisc below an already deep parent.
Store the hierarchy depth in struct Qdisc and update it when qdiscs are grafted. Reject new child qdiscs once the parent is already at the maximum allowed depth.
Which versions are affected by CVE-2026-74663?
How do I fix CVE-2026-74663?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-74663 being exploited?
There is no known exploitation of CVE-2026-74663 in the wild and no public exploit code.
Sources
Also known as AZL-97095, BELL-CVE-2026-74663, DEBIAN-CVE-2026-74663, GHSA-qwcm-6g6c-27vm, UBUNTU-CVE-2026-74663.