High 7.8Published Feb 18, 2025

CVE-2025-21703netem: Update sch->q.qlen before qdisc_tree_reduce_backlog()

Updated under an hour ago (Oct 27, 2026, 12:50 AM ET)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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: 7.8 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-416
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Modified
Record last updated: Oct 14, 2026
First seen by InfoSec Signals: Oct 14, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from 83c6ab12f08dcc09d4c5ac86fdb89736b28f1d31 before e395fec75ac2dbffc99b4bce57b7f1f3c5449f2c; 216509dda290f6db92c816dd54b83c1df9da9e76 builds before 7f31d74fcc556a9166b1bb20515542de7bb939d1; from c2047b0e216c8edce227d7c42f99ac2877dad0e4 before 98a2c685293aae122f688cde11d9334dddc5d207; 10df49cfca73dfbbdb6c4150d859f7e8926ae427 builds before 7b79ca9a1de6a428d486ff52fb3d602321c08f55; 3824c5fad18eeb7abe0c4fc966f29959552dca3e builds before 1f8e3f4a4b8b90ad274dfbc66fc7d55cb582f4d5; from 356078a5c55ec8d2061fcc009fb8599f5b0527f9 before 6312555249082d6d8cc5321ff725df05482d8b83; from f8d4bc455047cf3903cd6f85f49978987dbb3027 before 839ecc583fa00fab785fde1c85a326743657fd32; from f8d4bc455047cf3903cd6f85f49978987dbb3027 before 638ba5089324796c2ee49af10427459c2de35f71; and 6 more ranges	CNA record
Siemens SIMATIC S7-1500 TM MFP - BIOS siemens:simatic_s7_1500_tm_mfp_bios (from the name)	all versions	CISA ADP
Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem siemens:simatic_s7_1500_tm_mfp_gnu_linux_subsystem (from the name)	all versions	CISA ADP
linux linux_kernel linux:linux_kernel	from 5.4.288 before 5.4.291; from 5.10.232 before 5.10.235; from 5.15.175 before 5.15.179; from 6.1.121 before 6.1.129; from 6.6.67 before 6.6.78; from 6.12.6 before 6.12.14; from 6.13 before 6.13.3; 6.14	NVD

References

References

https://git.kernel.org/stable/c/e395fec75ac2dbffc99b4bce57b7f1f3c5449f2c	patch
https://git.kernel.org/stable/c/7f31d74fcc556a9166b1bb20515542de7bb939d1	patch
https://git.kernel.org/stable/c/98a2c685293aae122f688cde11d9334dddc5d207	patch
https://git.kernel.org/stable/c/7b79ca9a1de6a428d486ff52fb3d602321c08f55	patch
https://git.kernel.org/stable/c/1f8e3f4a4b8b90ad274dfbc66fc7d55cb582f4d5	patch
https://git.kernel.org/stable/c/6312555249082d6d8cc5321ff725df05482d8b83	patch
https://git.kernel.org/stable/c/839ecc583fa00fab785fde1c85a326743657fd32	patch
https://git.kernel.org/stable/c/638ba5089324796c2ee49af10427459c2de35f71	patch
https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
https://cert-portal.siemens.com/productcert/html/ssa-503939.html
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The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.