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CVE-2026-31684

5.5 · MEDIUM

In the Linux kernel, the following vulnerability has been resolved: net: sched: act_csum: validate nested VLAN headers tcf_csum_act() walks nested VLAN headers directly from skb->data when an skb…

Published Apr 25, 2026EPSS 0.12%

Overview

CVE-2026-31684 is a medium-severity vulnerability. It was published on April 25, 2026 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:

net: sched: act_csum: validate nested VLAN headers

tcf_csum_act() walks nested VLAN headers directly from skb->data when an

skb still carries in-payload VLAN tags. The current code reads

vlan->h_vlan_encapsulated_proto and then pulls VLAN_HLEN bytes without

first ensuring that the full VLAN header is present in the linear area.

If only part of an inner VLAN header is linearized, accessing

h_vlan_encapsulated_proto reads past the linear area, and the following

skb_pull(VLAN_HLEN) may violate skb invariants.

Fix this by requiring pskb_may_pull(skb, VLAN_HLEN) before accessing and

pulling each nested VLAN header. If the header still is not fully

available, drop the packet through the existing error path.

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/0410c619e86551677fb79887a38eccad3f5a0725Refgit.kernel.org/stable/c/3d165d975305cf76ff0b10a3c798fb31e5f5f9a5Refgit.kernel.org/stable/c/46c07ad50fa2f4ba7663ee1b72b75ad7ad45cf09Refgit.kernel.org/stable/c/886469b6455611a511aa6013e957e15e50577513Refgit.kernel.org/stable/c/a69738efea0996d05a3c7d2178551b891744df1bRefgit.kernel.org/stable/c/c842743d073bdd683606cb414eb0ca84465dd834Refgit.kernel.org/stable/c/eb3765b90eb8f2a3d6310a80c14a9e57ec4267a2Refgit.kernel.org/stable/c/ec4930979b3f7bbeb7af5744599fc6603a4dba62

How CyberStrike helps

Frequently asked questions

What is CVE-2026-31684?

CVE-2026-31684 is a medium-severity vulnerability. It was published on April 25, 2026 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2026-31684?

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-2026-31684?

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-2026-31684?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-31684 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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