Threats Tagged 'cve-2026-63569'

CVE-2026-63569 is a critical vulnerability in the DHAgreement.CalculateAgreement method of the Legion of the Bouncy Castle Inc. bc-csharp library before version 2.7.0. It involves improper input validation in the MTI/A0 two-pass Diffie-Hellman key agreement, allowing an attacker to manipulate the agreed value and potentially recover the local static private key under certain conditions. This affects only applications that directly call DHAgreement.

Improper input validation in DHAgreement.CalculateAgreement (MTI/A0 two-pass Diffie-Hellman) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an on-path attacker to make the local party compute an agreed value the attacker already knows, defeating the key authentication MTI/A0 is meant to provide. It also allows a malicious peer to learn the local static private key modulo the small factors of p-1, and to recover it entirely in groups with many such factors. The attack uses a crafted out-of-range or small-order ephemeral value, and works because that value is raised to the static private key without the range and subgroup-membership checks applied to DH public keys. Only applications that call DHAgreement directly are affected.