Affects Cisco Catalyst 9000 series; DoS via VLAN BOOTP leakage could disrupt large networks.
CVE-2026-20084
Unauthenticated DoS via BOOTP VLAN leakage on Cisco IOS XE DHCP snooping.
Is CVE-2026-20084 being exploited?
Not confirmed. CVE-2026-20084 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.35% probability of exploitation in the next 30 days.
How severe is CVE-2026-20084?
CVE-2026-20084 is rated High with a CVSS score of 8.6. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-20084?
Not known from our data. No patch reference has been recorded for CVE-2026-20084, which is not the same as no patch existing — a fix may have shipped without a tagged reference, or after this record was written. The vendor advisory is the only authority on whether a fix exists, and mitigations may be available regardless.
What does CVE-2026-20084 affect?
CVE-2026-20084 affects Cisco Catalyst 9000 Series Switches, Cisco IOS XE DHCP Snooping. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-20084?
Apply vendor workarounds; monitor BOOTP traffic; patch when available
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthenticated remote DoS by forwarding BOOTP across VLANs, causing high CPU and device unreachability.
Immediate action required
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As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.