CVE-2026-98013 PUBLISHED

net/sched: fq_pie: clamp quantum in change path

Assigner: Linux
Reserved: 25.09.2026 Published: 25.09.2026 Updated: 25.09.2026

In the Linux kernel, the following vulnerability has been resolved:

net/sched: fq_pie: clamp quantum in change path

fq_pie_change() accepts any quantum value from userspace, including 1. With a crafted size table qdisc_pkt_len reaches ~2 GiB, so quantum=1 makes the deficit-refill loop spin ~2^31 times under the qdisc lock (a soft lockup / denial of service).

Add max(256U, ...) matching fq_codel_change().

Conditions to recreate the bug: CONFIG_NET_SCH_FQ_PIE=y. Requires CAP_NET_ADMIN (namespace-local via unshare -Urn suffices).

tc qdisc add dev dummy0 root fq_pie tc qdisc change dev dummy0 root fq_pie quantum 1 stab data 32768 size_log 15 cell_log 0

Product Status

Vendor Linux
Product Linux
Versions Default: unaffected
  • affected from ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to f90fe65b977e7aa9eb302230a09eb18f8c32ceaa (excl.)
  • affected from ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to c11e3a39807eb5a200445ae9082843ab86800415 (excl.)
  • affected from ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to 6655b56e2801008566c594ef231f6c7b3f716c61 (excl.)
  • affected from ec97ecf1ebe485a17cd8395a5f35e6b80b57665a to 4864f58c53eb47257d55e01f47d4a9f355f7f970 (excl.)
Vendor Linux
Product Linux
Versions Default: affected
  • Version 5.6 is affected
  • unaffected from 0 to 5.6 (excl.)
  • unaffected from 6.12.111 to 6.12.* (incl.)
  • unaffected from 6.18.53 to 6.18.* (incl.)
  • unaffected from 7.2.7 to 7.2.* (incl.)
  • unaffected from 7.3-rc3 to * (incl.)

References