CVE-2024-46800: sch/netem: fix use after free in netem_dequeue

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-09-18 · updated 2026-08-04
Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: sch/netem: fix use after free in netem_dequeue If netem_dequeue() enqueues packet to inner qdisc and that qdisc returns __NET_XMIT_STOLEN. The packet is dropped but qdisc_tree_reduce_backlog() is not called to update the parent's q.qlen, leading to the similar use-after-free as Commit e04991a48dbaf382 ("netem: fix return value if duplicate enqueue fails") Commands to trigger KASAN UaF: ip link add type dummy ip link set lo up ip link set dummy0 up tc qdisc add dev lo parent root handle 1: drr tc filter add dev lo parent 1: basic classid 1:1 tc class add dev lo classid 1:1 drr tc qdisc add dev lo parent 1:1 handle 2: netem tc qdisc add dev lo parent 2: handle 3: drr tc filter add dev lo parent 3: basic classid 3:1 action mirred egress redirect dev dummy0 tc class add dev lo classid 3:1 drr ping -c1 -W0.01 localhost # Trigger bug tc class del dev lo classid 1:1 tc class add dev lo classid 1:1 drr ping -c1 -W0.01 localhost # UaF

Affected products

Linux kernel: from 3.3 before 4.19.322; from 4.20 before 5.4.284; from 5.5 before 5.10.226; from 5.11 before 5.15.167; from 5.16 before 6.1.110; from 6.2 before 6.6.51 — fixed in 4.19.322, 5.10.226, 5.15.167, 5.4.284, 6.1.110, 6.10.10

How to fix

Upgrade to a fixed version: Linux kernel 4.19.322, 5.10.226, 5.15.167, 5.4.284. Check the vendor advisory for mitigations.

References

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