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CVE-2021-47222

7.8 · HIGH

In the Linux kernel, the following vulnerability has been resolved: net: bridge: fix vlan tunnel dst refcnt when egressing The egress tunnel code uses dst_clone() and directly sets the result whi…

Published May 21, 2024CWE-416EPSS 0.25%

Overview

CVE-2021-47222 is a high-severity vulnerability. It was published on May 21, 2024 and has a CVSS 3.1 base score of 7.8 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. 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:

net: bridge: fix vlan tunnel dst refcnt when egressing

The egress tunnel code uses dst_clone() and directly sets the result

which is wrong because the entry might have 0 refcnt or be already deleted,

causing number of problems. It also triggers the WARN_ON() in dst_hold()[1]

when a refcnt couldn't be taken. Fix it by using dst_hold_safe() and

checking if a reference was actually taken before setting the dst.

[1] dmesg WARN_ON log and following refcnt errors

WARNING: CPU: 5 PID: 38 at include/net/dst.h:230 br_handle_egress_vlan_tunnel+0x10b/0x134 [bridge]

Modules linked in: 8021q garp mrp bridge stp llc bonding ipv6 virtio_net

CPU: 5 PID: 38 Comm: ksoftirqd/5 Kdump: loaded Tainted: G W 5.13.0-rc3+ #360

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014

RIP: 0010:br_handle_egress_vlan_tunnel+0x10b/0x134 [bridge]

Code: e8 85 bc 01 e1 45 84 f6 74 90 45 31 f6 85 db 4

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/25053a8404ba17ca48f5553d487afc1882e9f56cRefgit.kernel.org/stable/c/42020f7f37a90d24b9551f5f7eba3f7c7c102968Refgit.kernel.org/stable/c/79855be6445b6592bddb7bd7167083ec8cdbd73fRefgit.kernel.org/stable/c/84fc1c944e45ab317e2e70a0e7f76fa2a5e43b6eRefgit.kernel.org/stable/c/cfc579f9d89af4ada58c69b03bcaa4887840f3b3Refgit.kernel.org/stable/c/fc7fdd8c5c2ad2fe3e297698be9d4dbe4a4e0579Refgit.kernel.org/stable/c/25053a8404ba17ca48f5553d487afc1882e9f56cRefgit.kernel.org/stable/c/42020f7f37a90d24b9551f5f7eba3f7c7c102968Refgit.kernel.org/stable/c/79855be6445b6592bddb7bd7167083ec8cdbd73fRefgit.kernel.org/stable/c/84fc1c944e45ab317e2e70a0e7f76fa2a5e43b6e

How CyberStrike helps

Frequently asked questions

What is CVE-2021-47222?

CVE-2021-47222 is a high-severity vulnerability. It was published on May 21, 2024 and has a CVSS 3.1 base score of 7.8 (HIGH).

How severe is CVE-2021-47222?

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2021-47222?

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-2021-47222?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-47222 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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