Global DNS Crash Triggers Reboot Loops Across Cisco Small Business Switches
ID: 076ddba4-f4fc-50ea-80a1-7f1f723b1aae
STIX ID: report--076ddba4-f4fc-50ea-80a1-7f1f723b1aae
Feed Name: The Cyber Express
Threat Score
A defect in the DNS client on multiple Cisco Small Business switch families (CBS250, C1200, CBS350, SG350, SG550X, and related Catalyst 1200/1300) caused devices worldwide to enter reboot loops and generate core dumps on January 8, 2026 when certain DNS or time-server lookups failed or returned unexpected responses; administrators stabilized networks by disabling DNS/SNTP or blocking outbound DNS while Cisco had acknowledged the issue privately but had not issued a public advisory or patch.
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