Cisco Umbrella customers experienced inability to access certain Akamai-hosted domains over approximately 7 days, caused by DNS responses from Akamai IPv6 name servers exceeding 1410 bytes being truncated, resulting in SERVFAIL errors from Cisco resolvers. A partial workaround was implemented allowing affected domains to be bypassed from Cisco DNS, while full resolution was coordinated with Akamai. The issue was fully resolved on October 9, 2026, with all services returning to normal operation.
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The issue affecting access to some Akamai-hosted domains through Cisco Umbrella has been resolved. All services are now operating normally.
We apologize for any inconvenience caused and thank you for your patience.
We have implemented a partial workaround for the currently identified affected domains. Customers should begin seeing restored access to these domains.
The underlying issue has not been fully resolved, and other Akamai-hosted domains may continue to return SERVFAIL responses. We are monitoring the effectiveness of this mitigation and continuing to work with Akamai toward a full resolution.
Customers who continue to experience issues can use the previously provided workaround to bypass affected domains from Cisco DNS. Additional updates will be provided as new information becomes available.
We have identified that the issue occurs with domains hosted on Akamai IPv6 name servers that return a DNS response that is larger than 1410 bytes. These responses are being truncated which causes a Servfail response from the Cisco resolvers. We are continuing to work with Akamai to resolve this issue, we have the following proposed workaround.
Work Around
You can bypass the impacted domains from Cisco DNS. This can be performed with the Domain Management configuration for managed devices (Virtual Appliances and Roaming Clients) and with conditional forwarding rules on local DNS servers externally forwarding to Cisco DNS.
Customers using Cisco Umbrella might be unable to access some Akamai-hosted domains due to DNSSEC validation failure.Our teams are investigating and working to restore access. We will provide updates as more information becomes available.
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