CVE-2026-89562 Linux CVE debrief

Who should care

Linux kernel administrators and developers, particularly those working with ip6_gre tunnels, should assess and verify the configuration of their tunnels to ensure correct hardware header length settings. This includes verifying and correcting dev->hard_header_len settings for NBMA tunnels and reviewing and updating Linux kernel versions to ensure the fix is applied. Operators, platform managers, and security teams should also review the vulnerability and

Why it matters

The vulnerability in the Linux kernel's ip6_gre module requires verification of hardware header length configurations for NBMA tunnels to prevent potential issues with network communication.

• Verify hardware header length configuration for ip6_gre tunnels
• Assess potential impact on network communication
• Review Linux kernel versions for fix

Technical summary

The Linux kernel vulnerability affects the ip6_gre module, specifically in the way it handles hardware header length for NBMA tunnels. The issue arises from the incorrect accumulation of the lower device's hardware header length into dev->hard_header_len when header_ops is set. This could lead to incorrect hardware header length for NBMA tunnels. Linux kernel administrators and developers should assess and verify the configuration of their tunnels to ensure correct hardware header length settings. The vulnerability requires verification of hardware header length configurations for NBMA tunnels to prevent potential issues with network communication.

Defensive priority

Assess and verify the configuration of ip6_gre tunnels, particularly for NBMA tunnels, and ensure that the hardware header length is correctly set.

Recommended defensive actions

• Assess ip6_gre tunnel configurations for potential hardware header length issues
• Verify and correct dev->hard_header_len settings for NBMA tunnels
• Review and update Linux kernel versions to ensure the fix is applied
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record and source item provide information on the vulnerability in the Linux kernel's ip6_gre module. Details on exploitation, impact, and remediation are limited. The vulnerability affects the way hardware header length is handled for NBMA tunnels. The issue arises from the incorrect accumulation of the lower device's hardware header length into dev->hard_header_len when header_ops is set. This could lead to incorrect hardware header length for NBMA tunnels. Linux kernel administrators and developers, particularly those

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.