CVE-2026-23735 is a concurrency-related vulnerability classified under CWE-362 (Race Condition) found in graphql-hive's graphql-modules library, specifically in versions >=2.2.1 and <2.4.1, and >=3.0.0 and <3.1.1. The issue occurs when multiple parallel GraphQL requests invoke the same service that uses the @ExecutionContext() decorator to inject request-specific context, such as authentication tokens. Due to improper synchronization, the context data from concurrent requests can become intermingled, causing one request to potentially access or leak another request's sensitive data. This flaw undermines the confidentiality and integrity of data handled by backend APIs accessed through these services. The vulnerability is exploitable remotely without authentication or user interaction, increasing its risk profile. The CVSS 4.0 base score is 8.7 (high), reflecting network attack vector, low attack complexity, no privileges or user interaction required, and high impact on confidentiality. The flaw was addressed in graphql-modules versions 2.4.1 and 3.1.1 by correcting the synchronization mechanism to isolate request contexts properly. No known exploits are reported in the wild yet, but the potential for data leakage in multi-tenant or high-concurrency environments is significant. Organizations using affected versions should prioritize patching and review their GraphQL service implementations for similar concurrency issues.

For European organizations, this vulnerability poses a significant risk to the confidentiality and integrity of sensitive data processed via GraphQL APIs, particularly in environments with high concurrency or multi-tenant architectures. Unauthorized access or leakage of authentication tokens and backend API data could lead to data breaches, regulatory non-compliance (e.g., GDPR violations), and reputational damage. The impact is amplified for sectors relying heavily on GraphQL for internal or customer-facing services, such as finance, healthcare, and e-commerce. Additionally, the ease of remote exploitation without authentication means attackers can leverage this flaw to escalate privileges or pivot within networks. The vulnerability could disrupt operations if exploited at scale, causing service trust issues and potential downtime during incident response.

1. Upgrade graphql-modules to versions 2.4.1 or 3.1.1 immediately to apply the official fix. 2. Audit all GraphQL services using @ExecutionContext() to ensure context data is not shared or mixed across concurrent requests. 3. Implement strict concurrency controls and synchronization mechanisms in custom GraphQL service code to prevent race conditions. 4. Conduct thorough code reviews and dynamic testing focusing on concurrency and context isolation. 5. Monitor GraphQL API logs for anomalous access patterns indicative of context leakage or unauthorized data access. 6. Employ runtime application self-protection (RASP) or Web Application Firewalls (WAFs) with GraphQL-specific rules to detect and block suspicious parallel request patterns. 7. Educate developers on secure handling of request context in asynchronous environments. 8. Consider isolating critical services or sensitive data access behind additional authentication or token validation layers to reduce risk.