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In some circumstances, when DNSdist is configured to allow an unlimited number of queries on a single, incoming TCP connection from a client, an attacker can cause a denial of service by crafting a TCP exchange that triggers an exhaustion of the stack and a crash of DNSdist, causing a denial of service.
The remedy is: upgrade to the patched 1.9.10 version.
A workaround is to restrict the maximum number of queries on incoming TCP connections to a safe value, like 50, via the setMaxTCPQueriesPerConnection setting.
We would like to thank Renaud Allard for bringing this issue to our attention.
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Alpine Linux | — | Upgrade dnsdist | Aug 8, 2025 | May 20, 2025 |
| Debian | — | Upgrade dnsdist | May 28, 2025 | May 20, 2025 |
| Suse | — | Upgrade dnsdist | Dec 5, 2025 | May 29, 2025 |
| Ubuntu | — | Upgrade dnsdist (Ubuntu Pro)Upgrade dnsdist | Feb 13, 2026 | May 20, 2025 |
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