CVE-2026-98065 Linux CVE debrief

Who should care

Linux kernel developers, administrators who use BPF-based tools and applications, and security teams should be aware of this vulnerability and take steps to mitigate it. Affected operators should review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance, and plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.

Why it matters

This vulnerability in the Linux kernel's BPF subsystem allows for a denial-of-service (DoS) attack when a key-less BTF is used for hash maps. Linux kernel developers and administrators who use BPF-based tools and applications should be aware of this vulnerability and take steps to mitigate it.

• Denial-of-service (DoS) attack
• Potential system crashes or instability

Technical summary

The vulnerability is caused by the fact that the map_check_btf() function allows a key-less BTF only for maps that have a ->map_check_btf callback, and leaves the actual decision to that callback. Hash maps used to have no ->map_check_btf, so a key-less BTF was rejected outright. However, after htab and rhtab gained a ->map_check_btf to register a dtor, a key-less hash map now passes map_check_btf() and gets created. Reading it back through bpffs feeds the key type_id 0 into btf_type_seq_show(); btf_type_by_id() returns the void type, kind_ops[BTF_KIND_UNKN] is NULL, and btf_type_show() dereferences it, causing a null pointer dereference.

Defensive priority

Medium

Recommended defensive actions

• Review and update Linux kernel to the latest version
• Implement BPF subsystem security best practices
• Monitor system for suspicious activity
• 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 vulnerability was introduced in the Linux kernel and is related to the BPF subsystem. The CVE record and NVD vulnerability detail page provide information about the vulnerability. Linux kernel developers and administrators should verify the affected versions and configurations, review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance, and plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.

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.