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CVE-2026-23074

Vulnérabilité élevée dans Linux (Linux)

CVSS 7.8 · Élevée
EPSS 0.2%
Linux•Linux•Versions : <=6.1.*, <=6.12.*, 2.6.12, <16ed73c1282d376b956bff23e5139add061767ba, 0, <73d970ff0eddd874a84c953387c7f4464b705fc6, 5.15.199, <2.6.12, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, <dad49a67c2d817bfec98e6e45121b351e3a0202c, <4c7e8aa71c9232cba84c289b4b56cba80b280841, <=5.10.*, <=6.6.*, 5.10.249, 6.18.8, 6.1.162, <=6.18.*, <ae810e6a8ac4fe25042e6825d2a401207a2e41fb, <50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b, 6.12.68, <=*, <=5.15.*, 6.19, <0686bedfed34155520f3f735cbf3210cb9044380, 6.6.122

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.

Gravité et risque d'exploitation

CVE-2026-23074 obtient un score CVSS de 7.8/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.16 %, ce qui la place devant 4.4 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions <=6.1.*, <=6.12.*, 2.6.12, <16ed73c1282d376b956bff23e5139add061767ba, 0, <73d970ff0eddd874a84c953387c7f4464b705fc6, 5.15.199, <2.6.12, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, <dad49a67c2d817bfec98e6e45121b351e3a0202c, <4c7e8aa71c9232cba84c289b4b56cba80b280841, <=5.10.*, <=6.6.*, 5.10.249, 6.18.8, 6.1.162, <=6.18.*, <ae810e6a8ac4fe25042e6825d2a401207a2e41fb, <50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b, 6.12.68, <=*, <=5.15.*, 6.19, <0686bedfed34155520f3f735cbf3210cb9044380, 6.6.122) est présent sur votre parc.
  • Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
  • À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
  • Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

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