CVE-2026-98851 Linux CVE debrief

Who should care

Linux kernel developers and maintainers, as well as users and administrators of systems running the Linux kernel, should be aware of this vulnerability and take steps to apply the patches or update their kernels to a version that includes the fix.

Why it matters

The CVE-2026-98851 vulnerability in the Linux kernel's netfilter subsystem can lead to a reference leak, potentially causing denial of service. Linux kernel developers, maintainers, and users should be aware of this issue and take steps to apply patches or update their kernels.

• Verify flowtable reference counting to prevent denial of service.
• Assess exposure of Linux kernel deployments to potential reference leaks.
• Prioritize patching or updating Linux kernel versions to prevent exploitation.

Technical summary

The vulnerability is caused by a reference leak in the nft_flow_offload_init() function. When nf_ct_netns_get() returns an error, the function fails to decrement the flowtable use count, leading to a reference leak. This can prevent the flowtable from being removed, even after all rules referencing it have been deleted. The issue arises in the Linux kernel's netfilter subsystem, specifically in the nft_flow_offload component, and can lead to denial of service. Linux kernel developers, maintainers, and users should be aware of this issue and take steps to apply patches or update their kernels to a version that includes the fix.

Defensive priority

Medium

Recommended defensive actions

• Review and apply patches provided by Linux kernel maintainers to address the vulnerability.
• Verify flowtable reference counting to prevent denial of service.
• Assess exposure of Linux kernel deployments to potential reference leaks.
• Prioritize patching or updating Linux kernel versions to prevent exploitation.
• Monitor systems for suspicious activity related to the netfilter subsystem.
• Ensure that Linux kernel updates include the fix for the vulnerability.
• Track exceptions and retest remediated assets to confirm resolution.

Evidence notes

The CVE record and associated source item provide details on the vulnerability, including its description, affected versions, and references to source code changes. However, the record does not provide explicit information on exploitation or impact.

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.