CVE-2026-23074High· 7.8▾ TwilightIn 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 const…
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 42.9 · likelihood 0 · exploitation 0
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Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake.
Exploit-prediction probability, daily snapshots since Aug 1.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
Last analysed / modified upstream
0.1%
0.1% → 0.2%
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 [email protected] 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.
linux_kernel >= 2.6.12.1, < 5.10.249linux_kernel >= 5.11, < 5.15.199linux_kernel >= 5.16, < 6.1.162linux_kernel >= 6.2, < 6.6.122linux_kernel >= 6.7, < 6.12.68linux_kernel >= 6.13, < 6.18.8linux_kernel = 2.6.12linux_kernel = 6.19Upgrade past the affected range:
linux_kernel 6.18.8Connected by shared product, vendor, weakness, or advisory.
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