CVE-2025-37932 sch_htb: make htb_qlen_notify() idempotent
A flaw in the Linux kernel's HTB scheduler could cause a warning or instability when handling queue length notifications, potentially leading to denial of service.
- 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-2025-37932?
CVE-2025-37932 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 20 May 2025. 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:
sch_htb: make htb_qlen_notify() idempotent
htb_qlen_notify() always deactivates the HTB class and in fact could trigger a warning if it is already deactivated. Therefore, it is not idempotent and not friendly to its callers, like fq_codel_dequeue().
Let's make it idempotent to ease qdisc_tree_reduce_backlog() callers' life.
Which versions are affected by CVE-2025-37932?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2025-37932?
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-2025-37932 being exploited?
There is no known exploitation of CVE-2025-37932 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as AZL-72826, BELL-CVE-2025-37932, DEBIAN-CVE-2025-37932, GHSA-h35m-jp6f-245x, ROOT-OS-DEBIAN-11-CVE-2025-37932, ROOT-OS-DEBIAN-12-CVE-2025-37932 and 2 more.