Twisted: DNS Response Spoofing in twisted.names Due to Missing Source Address Validation

Twisted is an event-based framework for internet applications, supporting Python 3.6+. Prior to 26.10.0rc1, twisted.names.dns.DNSDatagramProtocol accepts a UDP DNS response for a pending query when its 16-bit transaction ID matches but does not verify that the response came from the queried host and port. An attacker able to deliver a packet to the resolver's listening port with the correct transaction ID can inject a forged answer. The standard twisted.names.client.Resolver uses a new random source port for each query, increasing off-path attack complexity, while applications that reuse a DNSDatagramProtocol instance expose only the transaction-ID search space after the first query. A successful forgery can redirect hostname resolution and enable mail interception, server-side request forgery, or man-in-the-middle positioning. This issue is fixed in version 26.10.0rc1.

Source published

23 Oct 2026 20:21:54 UTC

Source modified

23 Oct 2026 20:21:54 UTC

Observed here

23 Oct 2026 21:48:20 UTC

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CVSS 3.1 · 3.1 CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N