CVE-2025-38107: net_sched: ets: fix a race in ets_qdisc_change()

Severity: high (CVSS 7.0 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-07-03 · updated 2026-10-15
Weakness: CWE-362

Description

In the Linux kernel, the following vulnerability has been resolved: net_sched: ets: fix a race in ets_qdisc_change() Gerrard Tai reported a race condition in ETS, 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.

Affected products

Debian Linux: 11.0
Linux kernel: from 5.4.213 before 5.5; from 5.10.142 before 5.10.239; from 5.15.66 before 5.15.186; from 5.19.8 before 6.0; from 6.0.1 before 6.1.142; from 6.2 before 6.6.94 — fixed in 5.10.239, 5.15.186, 5.5, 6.0, 6.1.142, 6.12.34

How to fix

Upgrade to a fixed version: Linux kernel 5.10.239, 5.15.186, 5.5, 6.0. Check the vendor advisory for mitigations.

References

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