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CVE-2021-47125

5.5 · MEDIUM

In the Linux kernel, the following vulnerability has been resolved: sch_htb: fix refcount leak in htb_parent_to_leaf_offload The commit ae81feb7338c ("sch_htb: fix null pointer dereference on a n…

Published Mar 15, 2024EPSS 0.19%

Overview

CVE-2021-47125 is a medium-severity vulnerability. It was published on March 15, 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:

sch_htb: fix refcount leak in htb_parent_to_leaf_offload

The commit ae81feb7338c ("sch_htb: fix null pointer dereference

on a null new_q") fixes a NULL pointer dereference bug, but it

is not correct.

Because htb_graft_helper properly handles the case when new_q

is NULL, and after the previous patch by skipping this call

which creates an inconsistency : dev_queue->qdisc will still

point to the old qdisc, but cl->parent->leaf.q will point to

the new one (which will be noop_qdisc, because new_q was NULL).

The code is based on an assumption that these two pointers are

the same, so it can lead to refcount leaks.

The correct fix is to add a NULL pointer check to protect

qdisc_refcount_inc inside htb_parent_to_leaf_offload.

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/2411c02d03892a5057499f8102d0cc1e0f852416Refgit.kernel.org/stable/c/944d671d5faa0d78980a3da5c0f04960ef1ad893Refgit.kernel.org/stable/c/2411c02d03892a5057499f8102d0cc1e0f852416Refgit.kernel.org/stable/c/944d671d5faa0d78980a3da5c0f04960ef1ad893

How CyberStrike helps

Frequently asked questions

What is CVE-2021-47125?

CVE-2021-47125 is a medium-severity vulnerability. It was published on March 15, 2024 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2021-47125?

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-2021-47125?

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-2021-47125?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-47125 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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