CVE-2025-37913 net_sched: qfq: Fix double list add in class with netem as child qdisc

High 7.8 Published 20 May 2025 Updated 15 Oct 2026

A double list addition in the Linux kernel QFQ scheduler with netem child qdiscs causes memory corruption, potentially leading to system crashes or code execution.

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-2025-37913?

CVE-2025-37913 is a high-severity memory corruption 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:

net_sched: qfq: Fix double list add in class with netem as child qdisc

As described in Gerrard's report [1], there are use cases where a netem child qdisc will make the parent qdisc's enqueue callback reentrant. In the case of qfq, there won't be a UAF, but the code will add the same classifier to the list twice, which will cause memory corruption.

This patch checks whether the class was already added to the agg->active list (cl_is_active) before doing the addition to cater for the reentrant case.

[1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/

Weakness: CWE-415

Which versions are affected by CVE-2025-37913?

It affects 2 products.

Products include Debian Debian Linux, Linux kernel.

How do I fix CVE-2025-37913?

Apply the vendor's patch.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2025-37913 being exploited?

There is no known exploitation of CVE-2025-37913 in the wild and no public exploit code.

All Debian Debian Linux vulnerabilities

Sources

Also known as BELL-CVE-2025-37913, DEBIAN-CVE-2025-37913, GHSA-5363-pqw5-qgr2, ROOT-OS-DEBIAN-11-CVE-2025-37913, ROOT-OS-DEBIAN-12-CVE-2025-37913, ROOT-OS-UBUNTU-2204-CVE-2025-37913 and 2 more.