CVE-2022-29185 is a vulnerability identified in the totp-rs library, a Rust implementation used to generate time-based one-time passwords (TOTP) for two-factor authentication (2FA). The flaw exists in versions prior to 1.1.0, where the token comparison function did not operate in constant time. This timing discrepancy can theoretically allow an attacker to perform a side-channel attack by measuring the time taken to compare tokens, thereby incrementally guessing the correct TOTP value within the valid time window. However, exploitation requires the attacker to already know the user's password, as the attack targets the token comparison step rather than bypassing the initial authentication. The vulnerability is categorized under CWE-208 (Observable Timing Discrepancy) and CWE-203 (Observable Discrepancy), indicating that the timing differences in token validation leak information that could be used to infer secret values. The patched version 1.1.0 of totp-rs addresses this by implementing constant-time comparison, eliminating timing side-channels. There are no known exploits in the wild, and no alternative workarounds exist aside from upgrading to the fixed version. This vulnerability primarily affects applications and services that integrate totp-rs for 2FA token validation, potentially exposing them to token guessing attacks if they use vulnerable versions.

For European organizations, the impact of this vulnerability is moderate but context-dependent. Since totp-rs is a Rust library, its usage is more prevalent in modern, security-conscious software projects, including fintech, government digital services, and critical infrastructure applications that implement TOTP-based 2FA. If an attacker can leverage the timing discrepancy to guess valid TOTP tokens, they could reuse tokens within the same time window, potentially bypassing the second factor of authentication. However, the prerequisite that the attacker must already know the user's password significantly limits the attack's standalone impact. The vulnerability could facilitate privilege escalation or lateral movement in scenarios where password compromise has occurred, weakening the overall security posture. European organizations handling sensitive personal data, financial transactions, or critical services relying on totp-rs for 2FA should consider this vulnerability seriously, as it undermines the integrity of multi-factor authentication. The absence of known exploits reduces immediate risk, but the theoretical attack vector remains a concern for high-security environments.

The primary and most effective mitigation is to upgrade all instances of totp-rs to version 1.1.0 or later, where constant-time comparison is implemented. Organizations should conduct an inventory of software components to identify any usage of totp-rs and verify the version in use. For applications where upgrading is not immediately feasible, implementing additional monitoring for anomalous authentication attempts and rate limiting TOTP validation requests can help reduce the risk of timing attacks. Developers should also review their authentication workflows to ensure no other timing side-channels exist and consider integrating hardware security modules (HSMs) or secure enclaves for cryptographic operations to further mitigate timing attacks. Finally, educating security teams about the importance of constant-time operations in cryptographic comparisons can prevent similar vulnerabilities in custom implementations.