CVE-2026-98010

What the bug is

drr_change_class() rejects explicit quantum==0 but falls back to psched_mtu() with no floor. With a crafted size table qdisc_pkt_len reaches ~2 GiB, so quantum=1 (or a zero psched_mtu on a headerless device) makes the deficit-refill loop spin under the qdisc lock. Add clamp_t(u32, quantum, 256, 1<<20) after the zero reject and on the fallback path. The explicit-zero reject is preserved. Conditions to recreate the bug: CONFIG_NET_SCH_DRR=y. Requires CAP_NET_ADMIN (namespace-local via unshare -Urn suffices). tc qdisc add dev dummy0 root drr tc class add dev dummy0 parent 1: classid 1:1 drr quantum 1

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

net/sched/sch_drr.c

What this is

TC subsystemMAINTAINERS section matched on net/sched/ · netdev@vger.kernel.org · Maintained

Kernel module

sch_drr

Check it on the machine

grep -w CONFIG_NET_SCH_DRR /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

lsmod | grep -w sch_drr

Prints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.

Show whether Debian builds this, per release

Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.

• bookworm, trixie, forky, sid, bookworm · linux-6.12m

m

a loadable module on every flavour - check lsmod, can be blacklisted

Build switch

CONFIG_NET_SCH_DRR

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-09-25 (24 days ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.18%, higher than 6.7% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

net/sched

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
2.6.29	5.10.271	e2297bbf9cf6
2.6.29	5.15.222	560794ee6e04
2.6.29	6.1.189	23fea7e6736b
2.6.29	6.6.158	b464affe9f9d
2.6.29	6.12.111	dc8b374214ef
2.6.29	6.18.53	d43cded350fe
2.6.29	7.2.7	8f756ae1c874
2.6.29	7.3	8382abec0f15

Debian advisories