CVE-2026-24785 identifies a cryptographic vulnerability in the Clatter library, a Rust implementation of the Noise protocol framework with post-quantum cryptography support. The flaw arises from non-compliance with the PSK validity rule defined in Section 9.3 of the Noise Protocol Framework. Specifically, certain post-quantum handshake patterns (`noise_pqkk_psk0`, `noise_pqkn_psk0`, `noise_pqnk_psk0`, `noise_pqnn_psk0`, and some hybrid variants) allow pre-shared key (PSK)-derived keys to be used for encryption without proper randomization via self-chosen ephemeral randomness. This misuse breaks the intended cryptographic guarantees by enabling key reuse scenarios that can be catastrophic, undermining confidentiality and integrity. The vulnerability is rooted in the use of a broken or risky cryptographic algorithm, categorized under CWE-327. The issue affects all Clatter versions prior to 2.2.0. The patched version 2.2.0 introduces runtime checks to detect and prevent the use of these insecure handshake patterns. Users are advised to avoid the vulnerable `*_psk0` handshake variants and carefully review any custom handshake patterns to ensure compliance with the PSK validity rule. Although no exploits have been observed in the wild, the vulnerability's high CVSS score (8.0) reflects its potential severity and ease of exploitation without authentication or user interaction.

For European organizations, the vulnerability poses a significant risk to the confidentiality and integrity of communications secured using the Clatter library with affected handshake patterns. Since Clatter is designed for no_std Rust environments and supports post-quantum cryptography, it is likely used in embedded systems, IoT devices, or security-sensitive applications adopting next-generation cryptographic protocols. Exploitation could lead to catastrophic key reuse, allowing attackers to decrypt or manipulate encrypted communications, potentially compromising sensitive data and critical infrastructure. This risk is heightened in sectors such as telecommunications, defense, finance, and critical infrastructure, where secure key exchange is paramount. The lack of required authentication or user interaction for exploitation increases the threat surface. Although no known exploits exist currently, the vulnerability's presence in cryptographic handshake protocols means that any interception or active man-in-the-middle attacks could be devastating. European organizations adopting post-quantum cryptography must be vigilant to prevent undermining their security posture due to this flaw.

1. Upgrade all Clatter library instances to version 2.2.0 or later, which includes runtime checks preventing insecure handshake patterns. 2. Immediately audit all usage of Noise protocol handshake patterns in your codebase, specifically identifying any use of `*_psk0` post-quantum variants and hybrid patterns. 3. Avoid using the vulnerable `noise_pqkk_psk0`, `noise_pqkn_psk0`, `noise_pqnk_psk0`, `noise_pqnn_psk0` handshake patterns entirely. 4. For custom handshake patterns, conduct a thorough cryptographic review to ensure compliance with the PSK validity rule (Noise Protocol Framework Section 9.3). 5. Implement network monitoring to detect anomalous handshake behavior or repeated key reuse attempts. 6. Engage cryptographic experts to validate the security of post-quantum handshake implementations in your environment. 7. Incorporate secure development lifecycle practices emphasizing cryptographic protocol compliance and regular dependency updates. 8. Coordinate with vendors and supply chain partners to confirm they have applied the patch or mitigations. 9. Consider additional layers of encryption or key management controls to mitigate potential exposure during transition.