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CVE-2021-46981

5.5 · MEDIUM

In the Linux kernel, the following vulnerability has been resolved: nbd: Fix NULL pointer in flush_workqueue Open /dev/nbdX first, the config_refs will be 1 and the pointers in nbd_device are sti…

Published Feb 28, 2024CWE-476EPSS 0.25%

Overview

CVE-2021-46981 is a medium-severity vulnerability. It was published on February 28, 2024 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.5, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

In the Linux kernel, the following vulnerability has been resolved:

nbd: Fix NULL pointer in flush_workqueue

Open /dev/nbdX first, the config_refs will be 1 and

the pointers in nbd_device are still null. Disconnect

/dev/nbdX, then reference a null recv_workq. The

protection by config_refs in nbd_genl_disconnect is useless.

[ 656.366194] BUG: kernel NULL pointer dereference, address: 0000000000000020

[ 656.368943] #PF: supervisor write access in kernel mode

[ 656.369844] #PF: error_code(0x0002) - not-present page

[ 656.370717] PGD 10cc87067 P4D 10cc87067 PUD 1074b4067 PMD 0

[ 656.371693] Oops: 0002 [#1] SMP

[ 656.372242] CPU: 5 PID: 7977 Comm: nbd-client Not tainted 5.11.0-rc5-00040-g76c057c84d28 #1

[ 656.373661] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014

[ 656.375904] RIP: 0010:mutex_lock+0x29/0x60

[ 656.376627] Code: 00 0f 1f 44 00 00 55 48 89 fd 48 83 05 6f d7 fe 08 01 e8 7a c3 f

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/1c4962df938891af9ab4775f5224ef8601764107Refgit.kernel.org/stable/c/54b78ba7e96e5fe1edb8054e375d31a6c0dc60dcRefgit.kernel.org/stable/c/79ebe9110fa458d58f1fceb078e2068d7ad37390Refgit.kernel.org/stable/c/b31d237796fd618379ec8e0f4de3370b5e4aeee7Refgit.kernel.org/stable/c/cde4b55cfb24522dcbba80bbdb0c082303e76c43Refgit.kernel.org/stable/c/1c4962df938891af9ab4775f5224ef8601764107Refgit.kernel.org/stable/c/54b78ba7e96e5fe1edb8054e375d31a6c0dc60dcRefgit.kernel.org/stable/c/79ebe9110fa458d58f1fceb078e2068d7ad37390Refgit.kernel.org/stable/c/b31d237796fd618379ec8e0f4de3370b5e4aeee7Refgit.kernel.org/stable/c/cde4b55cfb24522dcbba80bbdb0c082303e76c43

How CyberStrike helps

Frequently asked questions

What is CVE-2021-46981?

CVE-2021-46981 is a medium-severity vulnerability. It was published on February 28, 2024 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2021-46981?

This vulnerability has a CVSS 3.1 base score of 5.5, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2021-46981?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2021-46981?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-46981 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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