CVE-2025-21703

In the Linux kernel, the following vulnerability has been resolved: netem: Update sch->q.qlen before qdisc_tree_reduce_backlog() qdisc_tree_reduce_backlog() notifies parent qdisc only if child qdisc becomes empty, therefore we need to reduce the backlog of the child qdisc before calling it. Otherwise it would miss the opportunity to call cops->qlen_notify(), in the case of DRR, it resulted in UAF since DRR uses ->qlen_notify() to maintain its active list.

CVSS 3.1

7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS

0.3% chance of exploitation in the next 30 days; higher than 22% of CVEs (scores of 2026-10-25)

CWE

CWE-416

Published

2025-02-18

Modified

2026-10-15

Record from

the NVD, synced 2026-10-19

Affected

• linux:linux_kernel

References

• https://git.kernel.org/stable/c/1f8e3f4a4b8b90ad274dfbc66fc7d55cb582f4d5
• https://git.kernel.org/stable/c/6312555249082d6d8cc5321ff725df05482d8b83
• https://git.kernel.org/stable/c/638ba5089324796c2ee49af10427459c2de35f71
• https://git.kernel.org/stable/c/7b79ca9a1de6a428d486ff52fb3d602321c08f55
• https://git.kernel.org/stable/c/7f31d74fcc556a9166b1bb20515542de7bb939d1

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