CVE-2025-37913: net_sched: qfq: Fix double list add in class with netem as child qdisc
In the Linux kernel, the following vulnerability has been resolved:
netsched: 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 (clisactive) before doing the addition to cater for the reentrant case.
[1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
debian/linuxto a version that resolves this vulnerability.Fixed in 6.1.176-1Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.115-2Fixed in 7.2.12-1Fixed in 7.2.15-1
Event History
Frequently Asked Questions
What is the severity of CVE-2025-37913?
CVE-2025-37913 has been classified as a medium severity vulnerability in the Linux kernel.
How do I fix CVE-2025-37913?
To fix CVE-2025-37913, update your Linux kernel to the latest version where this vulnerability is patched.
What systems are affected by CVE-2025-37913?
CVE-2025-37913 affects various versions of the Linux kernel that utilize the net_sched and netem components.
What is the risk associated with CVE-2025-37913?
The risk associated with CVE-2025-37913 includes potential denial of service due to the reentrancy in the enqueue callback.
Is there a workaround for CVE-2025-37913?
Currently, there are no known workarounds for CVE-2025-37913, and it is advisable to apply the kernel update.