CVE-2025-37915: net_sched: drr: Fix double list add in class with netem as child qdisc

Severity: high (CVSS 7.0 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-05-20 · updated 2026-10-15
Weakness: CWE-415

Description

In the Linux kernel, the following vulnerability has been resolved: net_sched: drr: 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 drr, there won't be a UAF, but the code will add the same classifier to the list twice, which will cause memory corruption. In addition to checking for qlen being zero, this patch checks whether the class was already added to the active_list (cl_is_active) before adding to the list to cover for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/

Affected products

Linux kernel: from 5.0.1 before 5.4.294; from 5.5 before 5.10.238; from 5.11 before 5.15.182; from 5.16 before 6.1.138; from 6.2 before 6.6.90; from 6.7 before 6.12.28 — fixed in 5.10.238, 5.15.182, 5.4.294, 6.1.138, 6.12.28, 6.14.6

How to fix

Upgrade to a fixed version: Linux kernel 5.10.238, 5.15.182, 5.4.294, 6.1.138. Check the vendor advisory for mitigations.

References

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