Description
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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| PowerDNS | DNSdist | — | 1.9.10 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | dnsdist | 1.9.10-1 | — |
| Debian 13 | dnsdist | 1.9.10-1 | — |
| Debian 12 | dnsdist | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 25.10 | dnsdist | 1.9.10-1ubuntu0.1 | USN-8037-1 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 24.04 LTS | dnsdist | 1.8.3-2ubuntu0.1~esm1 | USN-8037-1 |
| Ubuntu Pro 22.04 LTS | dnsdist | 1.6.1-1ubuntu0.1~esm2 | USN-8037-1 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | dnsdist | 1.9.10-150700.3.3.1 | SUSE-SU-2025:01743-1 |
| SLES 15 SP6 | dnsdist | 1.8.0-150400.9.6.1 | SUSE-SU-2025:01745-1 |
| SLES 15 SP5 | dnsdist | 1.8.0-150400.9.6.1 | SUSE-SU-2025:01745-1 |
| SLES 15 SP4 | dnsdist | 1.8.0-150400.9.6.1 | SUSE-SU-2025:01745-1 |
| SLES 15 SP3 | dnsdist | 1.8.0-150100.3.8.1 | SUSE-SU-2025:01792-1 |
Show 7 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 15 SP5 | dnsdist | 1.8.0-150400.9.6.1 | SUSE-SU-2025:01745-1 |
| SLES for SAP 15 SP4 | dnsdist | 1.8.0-150400.9.6.1 | SUSE-SU-2025:01745-1 |
| SLE HPC 15 SP5 | dnsdist | 1.8.0-150400.9.6.1 | SUSE-SU-2025:01745-1 |
| SLE HPC 15 SP4 | dnsdist | 1.8.0-150400.9.6.1 | SUSE-SU-2025:01745-1 |
| SUSE Manager Server 4.3 | dnsdist | 1.8.0-150400.9.6.1 | SUSE-SU-2025:01745-1 |
| SUSE Manager Proxy 4.3 | dnsdist | 1.8.0-150400.9.6.1 | SUSE-SU-2025:01745-1 |
| SUSE Enterprise Storage 7.1 | dnsdist | 1.8.0-150100.3.8.1 | SUSE-SU-2025:01792-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 15.6 | dnsdist | 1.8.0-150400.9.6.1 | SUSE-SU-2025:01745-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | dnsdist | 1.9.10-r0 | — |
| Alpine v3.23 | dnsdist | 1.9.10-r0 | — |
| Alpine v3.22 | dnsdist | 1.9.10-r0 | — |
| Alpine v3.21 | dnsdist | 1.9.10-r0 | — |
Advisories 4
- USN-8037-1 dnsdist vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- SUSE-SU-2025:01745-1 Security update for dnsdist SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:01792-1 Security update for dnsdist SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:01743-1 Security update for dnsdist SUSE / openSUSE Security Updates · Feb 4, 2026