CVE-2021-33630 | NULL-ptr-deref in network sched

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.

Published: 2024-01-18 Last update: 2025-04-02 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-33630 is rated Low Risk (29.2/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.06%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-33630

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-10-03 0.05% 0.06% +0.02%
2 2025-09-30 0.05% 0.05% -0.00%
3 2025-04-03 — 0.05% —

Full EPSS history (6 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-33630

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 3.6 [email protected]
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 3.6 [email protected]

Weakness enumeration for CVE-2021-33630

OS Trackers for CVE-2021-33630

vendor priority summary link
debian not yet assigned CVE-2021-33630 not yet assigned priority: Debian including 1 source packages (linux), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-33630
redhat medium — https://access.redhat.com/security/cve/CVE-2021-33630
suse medium CVE-2021-33630 severity moderate: SUSE including 33 source package names (bpftool-4.18.0-193.el8, kernel-4.18.0-193.el8, …), 195 product×package rows across 40 product lines (SUSE CaaS Platform 4.0, SUSE Liberty Linux 8, … (40 product lines)): Known Not Affected 175, Fixed 20. https://www.suse.com/security/cve/CVE-2021-33630/
ubuntu medium CVE-2021-33630 medium priority: Ubuntu including 129 source packages (linux, linux-allwinner-5.19, …), 1024 status rows across 8 suites (bionic, focal, jammy, mantic, noble, trusty, upstream, xenial): DNE 699, ignored 129, not-affected 121, released 69, needs-triage 6. https://ubuntu.com/security/CVE-2021-33630

Affected software / configurations for CVE-2021-33630

Vendor Product Version Raw CPE
openatom openeuler >= 4.19.90, < 4.19.90-2401.3 cpe:2.3:o:openatom:openeuler:*:*:*:*:-:*:*:*

References for CVE-2021-33630

URL Tags
http://www.openwall.com/lists/oss-security/2024/01/30/10
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/2024/01/31/2
http://www.openwall.com/lists/oss-security/2024/01/31/3
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://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3e8b9bfa110896f95d602d8c98d5f9d67e41d78c
https://gitee.com/src-openeuler/kernel/pulls/1389 Release Notes
https://lists.debian.org/debian-lts-announce/2024/06/msg00020.html
https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2024-1030 Vendor Advisory
https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2024-1031 Vendor Advisory
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