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CVE-2026-23074— net/sched: Enforce that teql can only be used as root qdisc

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于未强制约束使用方式，可能导致队列状态不一致。

CVSS 7.8 · High EPSS 0.16% · P4

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 16

VendorProduct Version RangeStatus
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 73d970ff0eddd874a84c953387c7f4464b705fc6 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< ae810e6a8ac4fe25042e6825d2a401207a2e41fb affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< dad49a67c2d817bfec98e6e45121b351e3a0202c affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 0686bedfed34155520f3f735cbf3210cb9044380 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 4c7e8aa71c9232cba84c289b4b56cba80b280841 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 16ed73c1282d376b956bff23e5139add061767ba affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b affected
2.6.12 affected
… +8 more rows
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I. Basic Information for CVE-2026-23074

Vulnerability Information
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Vulnerability Title
net/sched: Enforce that teql can only be used as root qdisc
Source: CVE Program / CVE List V5
Vulnerability Description
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 <km.kim1503@gmail.com> 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于未强制约束使用方式，可能导致队列状态不一致。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 ~ 73d970ff0eddd874a84c953387c7f4464b705fc6 -
Linux Linux 2.6.12 -

II. Public POCs for CVE-2026-23074

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III. Intelligence Information for CVE-2026-23074

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Same Patch Batch · Linux · 2026-02-04 · 79 CVEs total

CVE-2026-23098 8.8 HIGH netrom: fix double-free in nr_route_frame()
CVE-2026-23066 7.8 HIGH rxrpc: Fix recvmsg() unconditional requeue
CVE-2026-23077 7.8 HIGH mm/vma: fix anon_vma UAF on mremap() faulted, unfaulted merge
CVE-2026-23105 7.8 HIGH net/sched: qfq: Use cl_is_active to determine whether class is active in qfq_rm_from_ag
CVE-2026-23103 7.8 HIGH ipvlan: Make the addrs_lock be per port
CVE-2026-23095 7.5 HIGH gue: Fix skb memleak with inner IP protocol 0.
CVE-2025-71192 7.0 HIGH ALSA: ac97: fix a double free in snd_ac97_controller_register()
CVE-2026-23063 uacce: ensure safe queue release with state management
CVE-2026-23065 platform/x86/amd: Fix memory leak in wbrf_record()
CVE-2026-23064 net/sched: act_ife: avoid possible NULL deref
CVE-2026-23067 iommu/io-pgtable-arm: fix size_t signedness bug in unmap path
CVE-2026-23059 scsi: qla2xxx: Sanitize payload size to prevent member overflow
CVE-2026-23058 can: ems_usb: ems_usb_read_bulk_callback(): fix URB memory leak
CVE-2026-23057 vsock/virtio: Coalesce only linear skb
CVE-2026-23056 uacce: implement mremap in uacce_vm_ops to return -EPERM
CVE-2025-71199 iio: adc: at91-sama5d2_adc: Fix potential use-after-free in sama5d2_adc driver
CVE-2025-71198 iio: imu: st_lsm6dsx: fix iio_chan_spec for sensors without event detection
CVE-2025-71197 w1: therm: Fix off-by-one buffer overflow in alarms_store
CVE-2026-23055 i2c: riic: Move suspend handling to NOIRQ phase
CVE-2026-23040 wifi: mac80211_hwsim: fix typo in frequency notification

Showing top 20 of 79 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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