CVE-2025-46712 is a vulnerability identified in the Erlang/OTP platform, specifically affecting the SSH implementation in versions prior to OTP-27.3.4, OTP-26.2.5.12, and OTP-25.3.2.21. Erlang/OTP is a widely used set of libraries and runtime system for the Erlang programming language, often employed in telecommunications, messaging systems, and distributed applications. The vulnerability arises from a failure to enforce strict key exchange (KEX) handshake hardening measures during the SSH connection establishment phase. Specifically, the affected versions allow optional messages to be exchanged during the handshake process, which deviates from expected behavior. This flaw enables a Man-in-the-Middle (MitM) attacker to inject these optional messages into the SSH handshake, potentially manipulating the connection setup. Although the vulnerability does not directly compromise confidentiality or availability, it impacts the integrity of the SSH handshake, which could be leveraged in more complex attack chains or to weaken the security guarantees of the SSH session. The issue has been addressed in the patched versions OTP-27.3.4, OTP-26.2.5.12, and OTP-25.3.2.21, which enforce stricter handshake validation to prevent message injection. The CVSS score is 3.7 (low severity), reflecting the limited impact and the requirement for network-level MitM capabilities and high attack complexity. No known exploits are currently reported in the wild.

For European organizations, the impact of this vulnerability is generally low but context-dependent. Erlang/OTP is integral to many telecom infrastructures, messaging platforms, and distributed systems, some of which are critical in sectors such as telecommunications, finance, and industrial control. A successful MitM attack during the SSH handshake could allow attackers to interfere with session establishment, potentially enabling further exploitation or surveillance if combined with other vulnerabilities or misconfigurations. However, the vulnerability does not directly expose sensitive data or cause denial of service. Organizations relying on Erlang/OTP for secure communications should consider the risk of targeted attacks, especially in environments where network-level adversaries exist or where SSH is used for critical administrative access. The low CVSS score suggests limited immediate risk, but the presence of this flaw could be a stepping stone in multi-stage attacks against critical infrastructure components prevalent in Europe.

European organizations should prioritize upgrading Erlang/OTP to the fixed versions: OTP-27.3.4, OTP-26.2.5.12, or OTP-25.3.2.21, depending on their current version. Beyond patching, network-level mitigations include enforcing strict SSH policies such as using certificate-based authentication, enabling SSH fingerprint verification, and employing network segmentation to limit exposure of SSH services to untrusted networks. Deploying intrusion detection systems (IDS) capable of detecting anomalous SSH handshake behaviors may help identify attempted MitM attacks exploiting this vulnerability. Additionally, organizations should conduct regular audits of Erlang/OTP deployments and SSH configurations to ensure compliance with security best practices. For critical systems, consider using out-of-band management channels or VPNs to reduce the risk of MitM attacks on SSH sessions. Finally, monitoring vendor advisories for any emerging exploit reports or additional patches is recommended.