CVE-2022-31069 is a vulnerability identified in the Finastra finastra-nodejs-libs, specifically affecting the NestJS Proxy module prior to version 0.7.0. NestJS Proxy is a module designed to facilitate decorating and proxying calls within NestJS applications. The vulnerability arises from the module's inability to control the forwarding of Authorization headers to backend services on a per-service basis. Before the patch, the library forwarded OAuth bearer access tokens indiscriminately to all proxied backend services configured by the application developer. This behavior could lead to sensitive token exposure to unauthorized backend services that should not receive such credentials, thereby violating the principle of least privilege and potentially enabling unauthorized access or misuse of sensitive tokens. The issue is classified under CWE-200, indicating exposure of sensitive information to unauthorized actors. The vulnerability was addressed in version 0.7.0 of the @finastra/nestjs-proxy package by introducing a configuration option, 'forwardToken', which allows developers to explicitly control whether Authorization headers are forwarded to each backend service. Additionally, users of the deprecated @ffdc/nestjs-proxy package are advised to migrate to the maintained @finastra/nestjs-proxy package to receive this and future security updates. There are no known exploits in the wild reported for this vulnerability as of the published date, June 15, 2022. However, the risk remains significant due to the potential for inadvertent token leakage in applications using vulnerable versions of the library.

For European organizations, the exposure of OAuth bearer tokens can have serious consequences. OAuth tokens often grant access to sensitive APIs and resources, including personal data protected under GDPR, financial information, or internal corporate services. Unauthorized access resulting from token leakage could lead to data breaches, unauthorized transactions, or lateral movement within networks. This is particularly critical for sectors such as finance, healthcare, and government services prevalent in Europe, where sensitive data protection is paramount. The inadvertent forwarding of tokens to unintended backend services could also undermine trust in application security and lead to regulatory penalties under GDPR for failure to adequately protect personal data. Moreover, organizations relying on Finastra's Node.js libraries for financial or enterprise applications may face increased risk if they have not updated to the patched version, especially given Finastra's significant presence in the European financial software market. Although no active exploits are known, the vulnerability's nature means that any compromised backend service receiving tokens could misuse them, amplifying the potential impact.

European organizations using the affected Finastra Node.js libraries should take immediate steps to mitigate this vulnerability. First, update all instances of @finastra/nestjs-proxy to version 0.7.0 or later to ensure the 'forwardToken' configuration option is available. Review all backend service configurations to explicitly disable forwarding of Authorization headers where not required, minimizing token exposure. For applications still using the deprecated @ffdc/nestjs-proxy package, migrate to the maintained @finastra/nestjs-proxy package promptly to receive security updates. Conduct a thorough audit of all services that receive proxied requests to verify they are authorized to handle OAuth tokens. Implement strict access controls and monitoring on backend services to detect any anomalous use of tokens. Additionally, consider implementing short-lived OAuth tokens and token revocation mechanisms to limit the window of exposure if tokens are leaked. Finally, incorporate this vulnerability into security awareness and development training to prevent similar misconfigurations in future deployments.