CVE-2026-98567 Linux CVE debrief

Who should care

System administrators and security teams responsible for managing Linux kernel-based systems should be aware of this vulnerability and take steps to mitigate it. They should review and apply the provided kernel patches to fix the vulnerability and ensure that the Linux kernel is updated to a version that includes the fix. Additionally, they should monitor the system for any suspicious activity that may be related to this vulnerability and review compensing

Why it matters

The Linux kernel vulnerability CVE-2026-98567 can cause an out-of-bounds write in the XPS map, potentially leading to a denial-of-service (DoS). System administrators and security teams should review and apply the provided kernel patches to fix the vulnerability.

• Denial-of-service (DoS) due to out-of-bounds write in XPS map
• Potential for system crashes or instability

Technical summary

The vulnerability is caused by the lack of proper cleanup of the dev->tc_to_txq[] and dev->prio_tc_map[] arrays when the number of traffic classes is reduced. This can lead to an out-of-bounds write in the XPS map, potentially causing a denial-of-service (DoS). The bug occurs when netdev_set_num_tc() lowers dev->num_tc without properly cleaning up the arrays, leaving leftover entries that can be accessed by netdev_txq_to_tc() and __netif_set_xps_queue(). To fix this, it's essential to ensure that the number of traffic classes is not reduced without properly cleaning up the arrays.

Defensive priority

Medium

Recommended defensive actions

• Review and apply the provided kernel patches to fix the vulnerability
• Ensure that the Linux kernel is updated to a version that includes the fix
• Monitor the system for any suspicious activity that may be related to this vulnerability
• 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
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance

Evidence notes

The vulnerability is caused by the lack of proper cleanup of the dev->tc_to_txq[] and dev->prio_tc_map[] arrays when the number of traffic classes is reduced. This can lead to an out-of-bounds write in the XPS map.

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.