cbcvebase.
CVE-2026-23074
published 2026-02-04

CVE-2026-23074: In the Linux kernel, the following vulnerability has been resolved: net/sched: Enforce that teql can only be used as root qdisc Design intent of teql is that…

PriorityP340high7.8CVSS 3.1
AVLACLPRLUINSUCHIHAH
EPSS
0.13%
3.3th percentile
In the Linux kernel, the following vulnerability has been resolved: net/sched: Enforce that teql can only be used as root qdisc Design intent of teql is that it is only supposed to be used as root qdisc. We need to check for that constraint. Although not important, I will describe the scenario that unearthed this issue for the curious. GangMin Kim managed to concot a scenario as follows: ROOT qdisc 1:0 (QFQ) ├── class 1:1 (weight=15, lmax=16384) netem with delay 6.4s └── class 1:2 (weight=1, lmax=1514) teql GangMin sends a packet which is enqueued to 1:1 (netem). Any invocation of dequeue by QFQ from this class will not return a packet until after 6.4s. In the meantime, a second packet is sent and it lands on 1:2. teql's enqueue will return success and this will activate class 1:2. Main issue is that teql only updates the parent visible qlen (sch->q.qlen) at dequeue. Since QFQ will only call dequeue if peek succeeds (and teql's peek always returns NULL), dequeue will never be called and thus the qlen will remain as 0. With that in mind, when GangMin updates 1:2's lmax value, the qfq_change_class calls qfq_deact_rm_from_agg. Since the child qdisc's qlen was not incremented, qfq fails to deactivate the class, but still frees its pointers from the aggregate. So when the first packet is rescheduled after 6.4 seconds (netem's delay), a dangling pointer is accessed causing GangMin's causing a UAF.

Affected

61 ranges· showing 25
VendorProductVersion rangeFixed in
debianlinux< linux 6.1.162-1 (bookworm)linux 6.1.162-1 (bookworm)
debianlinux-6.1< linux 6.1.162-1 (bookworm)linux 6.1.162-1 (bookworm)
linuxlinux
linuxlinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 73d970ff0eddd874a84c953387c7f4464b705fc673d970ff0eddd874a84c953387c7f4464b705fc6
linuxlinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < ae810e6a8ac4fe25042e6825d2a401207a2e41fbae810e6a8ac4fe25042e6825d2a401207a2e41fb
linuxlinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < dad49a67c2d817bfec98e6e45121b351e3a0202cdad49a67c2d817bfec98e6e45121b351e3a0202c
linuxlinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 0686bedfed34155520f3f735cbf3210cb90443800686bedfed34155520f3f735cbf3210cb9044380
linuxlinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 4c7e8aa71c9232cba84c289b4b56cba80b2808414c7e8aa71c9232cba84c289b4b56cba80b280841
linuxlinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 16ed73c1282d376b956bff23e5139add061767ba16ed73c1282d376b956bff23e5139add061767ba
linuxlinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel>= 0 < 5.10.249-15.10.249-1
linuxlinux_kernel>= 0 < 6.1.162-16.1.162-1
linuxlinux_kernel>= 0 < 6.12.69-16.12.69-1
linuxlinux_kernel>= 0 < 6.18.8-16.18.8-1

CVSS provenance

nvdv3.17.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
osv7.8HIGH
vendor_debian7.8HIGH
vendor_redhat7.8HIGH
vendor_ubuntu7.8HIGH
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