CVE-2025-21703 - CVE House
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Status published High CVE-2025-21703

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

Vulnerability Description

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.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

No credits recorded in the NVD database.

References

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Affected Vendor

Affected Software

Linux
Vulnerable Versions:
83c6ab12f08dcc09d4c5ac86fdb89736b28f1d31, 216509dda290f6db92c816dd54b83c1df9da9e76, c2047b0e216c8edce227d7c42f99ac2877dad0e4, 10df49cfca73dfbbdb6c4150d859f7e8926ae427, 3824c5fad18eeb7abe0c4fc966f29959552dca3e, 356078a5c55ec8d2061fcc009fb8599f5b0527f9, f8d4bc455047cf3903cd6f85f49978987dbb3027, 5.4.288, 5.10.232, 5.15.175, 6.1.121, 6.6.67, 6.12.6, 6.13, 0, 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.78, 6.12.14, 6.13.3, 6.14

Timeline

Official Publish: February 18th, 2025
Last Modified: May 23rd, 2026
Added to House: July 22nd, 2026

CVSS Vectors

V3: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weaknesses (CWE)

No CWE data available

MITRE ATT&CK TTPs

No associated TTPs found for this vulnerability.