In the Linux kernel, the following vulnerability has been resolved:

net_sched: red: fix a race in __red_change()

Gerrard Tai reported a race condition in RED, whenever SFQ perturb timer
fires at the wrong time.

The race is as follows:

CPU 0 CPU 1
[1]: lock root
[2]: qdisc_tree_flush_backlog()
[3]: unlock root
|
| [5]: lock root
| [6]: rehash
| [7]: qdisc_tree_reduce_backlog()
|
[4]: qdisc_put()

This can be abused to underflow a parent's qlen.

Calling qdisc_purge_queue() instead of qdisc_tree_flush_backlog()
should fix the race, because all packets will be purged from the qdisc
before releasing the lock.
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Fri, 04 Jul 2025 00:30:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

threat_severity

Moderate


Thu, 03 Jul 2025 09:00:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: net_sched: red: fix a race in __red_change() Gerrard Tai reported a race condition in RED, whenever SFQ perturb timer fires at the wrong time. The race is as follows: CPU 0 CPU 1 [1]: lock root [2]: qdisc_tree_flush_backlog() [3]: unlock root | | [5]: lock root | [6]: rehash | [7]: qdisc_tree_reduce_backlog() | [4]: qdisc_put() This can be abused to underflow a parent's qlen. Calling qdisc_purge_queue() instead of qdisc_tree_flush_backlog() should fix the race, because all packets will be purged from the qdisc before releasing the lock.
Title net_sched: red: fix a race in __red_change()
References

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2025-07-28T04:12:23.828Z

Reserved: 2025-04-16T04:51:23.985Z

Link: CVE-2025-38108

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2025-07-03T09:15:24.413

Modified: 2025-07-03T15:13:53.147

Link: CVE-2025-38108

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-07-03T00:00:00Z

Links: CVE-2025-38108 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2025-07-06T22:16:22Z