Kimi cli: Internationalized Domain Names in Applications (IDNA): Specially crafted inputs to idna.encode() can bypass CVE-2024-3651 fix (CVE-2026-45409)

CVE-2026-45409 is a denial-of-service vulnerability in the idna.encode() function used by kimi-cli, where specially crafted inputs that exploit the valid_contexto function can cause excessive resource consumption. This issue is a bypass of the previous fix for CVE-2024-3651, as the original remediation did not fully prevent processing of long inputs before length rejection. Starting with version 3.14, idna.encode() rejects long inputs early to minimize resource use, and version 3.15 extends this to other related functions. Without these patches, an attacker can supply arbitrarily large inputs that cause significant processing delays, leading to denial-of-service conditions.

An attacker can cause the idna.encode() function to consume significant CPU resources by providing specially crafted, excessively long inputs. This can lead to denial-of-service conditions in applications using vulnerable versions of kimi-cli. There is no impact on confidentiality or integrity, only availability is affected.

A fix is available and should be applied by updating to version 3.14 or later, which includes early rejection of long inputs to prevent excessive resource consumption. Alternatively, enforcing the domain name length limit of 253 characters before passing input to idna.encode() can mitigate the issue. Standard system updates on supported Ubuntu releases will apply the necessary patches.