CVE-2026-98013 Linux CVE debrief

Who should care

Linux kernel maintainers, administrators, and users of the fq_pie scheduler should assess exposure and apply patches to prevent potential denial of service issues. Operators of Linux-based systems, especially those with network scheduling configurations, should review their deployments for potential exposure and apply patches or mitigations as needed. Vulnerability management and security teams should prioritize patching and monitoring for this issue due

Why it matters

The Linux kernel fq_pie scheduler vulnerability can cause a denial of service (soft lockup) due to an infinite loop under the qdisc lock, requiring assessment and patching to prevent potential system instability.

• Denial of service (soft lockup) due to infinite loop under qdisc lock
• Potential system slowdown or instability due to excessive loop iterations

Technical summary

The fq_pie_change() function in the Linux kernel's fq_pie network scheduler did not clamp the quantum value, allowing a crafted size table to cause a denial of service (soft lockup) due to an infinite loop under the qdisc lock. The issue required CAP_NET_ADMIN privileges and CONFIG_NET_SCH_FQ_PIE=y configuration. This vulnerability can cause system instability and potential denial of service issues if not addressed. The Linux kernel maintainers have resolved this issue by adding a clamp to the quantum value in the fq_pie_change() function.

Defensive priority

Assess exposure and apply patches for Linux kernel fq_pie scheduler vulnerability

Recommended defensive actions

• Assess if Linux kernel fq_pie scheduler is used in your deployment
• Verify if CAP_NET_ADMIN privileges are required for the affected configuration
• Apply patches or updates provided by the Linux kernel maintainers
• Monitor for potential denial of service (soft lockup) issues
• 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 NVD entry provide details on the vulnerability, including its description and affected configurations. The fq_pie_change() function in the Linux kernel's fq_pie network scheduler did not clamp the quantum value, allowing a crafted size table to cause a denial of service (soft lockup) due to an infinite loop under the qdisc lock. The issue required CAP_NET_ADMIN privileges and CONFIG_NET_SCH_FQ_PIE=y configuration. Evidence is limited to public CVE and NVD sources.

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.