CVE-2026-52832 in Nuclio
Summary
by MITRE • 09/02/2026
Nuclio is a "Serverless" framework for Real-Time Events and Data Processing. Prior to version 1.16.5, Nuclio Dashboard exposes POST /api/functions without authentication by default (NOP auth mode). The spec.handler field (e.g., mymodule:myfunction) is parsed by functionconfig.ParseHandler() which splits on : only — no path validation is applied to the module portion. This issue has been patched in version 1.16.5.
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Analysis
by VulDB Data Team • 09/02/2026
The Nuclio serverless framework, designed for real-time event and data processing, contains a critical authentication bypass vulnerability that affects versions prior to 1.16.5. By default, the Nuclio Dashboard operates with no authentication required (NOP auth mode) when exposing the POST /api/functions endpoint. This configuration allows unauthenticated actors to interact directly with the function deployment API without providing valid credentials or session tokens. The absence of access control mechanisms on this specific endpoint creates a significant attack surface where malicious users can attempt to deploy, modify, or delete serverless functions within the cluster environment.
The technical root cause lies in how the framework parses the spec.handler field during function configuration processing. When a user submits a request containing a handler specification such as mymodule:myfunction, the system invokes the functionconfig.ParseHandler() method. This parsing logic strictly splits the input string on the colon delimiter to separate the module name from the function name. Crucially, there is no path validation or sanitization applied to the module portion of this split result. While the primary vulnerability identified in public disclosures relates to authentication bypass due to NOP auth mode, the lack of strict validation on handler inputs can also facilitate injection attacks if combined with other misconfigurations or downstream processing flaws that do not properly escape special characters within the parsed module name before execution.
The operational impact of this vulnerability is severe for any deployment running in default configurations. An attacker who gains network access to the Nuclio Dashboard API can deploy arbitrary code into the Kubernetes cluster hosting the serverless functions. This effectively results in remote code execution (RCE) with the privileges assigned to the service account associated with the dashboard or function runner. The compromise allows for data exfiltration, lateral movement within the container orchestration platform, and potential disruption of critical real-time processing pipelines. Since Nuclio is often used for high-throughput event handling, an attacker could also inject malicious logic into legitimate workflows, leading to supply chain compromises where trusted functions are replaced with backdoored versions that leak sensitive data or perform destructive actions.
This vulnerability aligns with CWE-287 Improper Authentication and CWE-434 Unrestricted Upload of File with Dangerous Type if the handler parsing flaw is exploited for code injection. In terms of the MITRE ATT&CK framework, this maps to T1505 Server Software Component which involves installing or deploying malicious components such as server-side plugins or extensions. The exploitation path also relates to T1078 Valid Accounts if an attacker leverages default credentials or NOP auth settings that are commonly found in development environments left exposed to production networks.
Mitigation strategies must prioritize immediate remediation of the authentication configuration and software versioning. Organizations should upgrade Nuclio to version 1.16.5 or later, where this specific issue has been patched by enforcing proper access controls on the API endpoints. For deployments that cannot be immediately upgraded, it is imperative to configure the dashboard to require valid authentication tokens rather than relying on NOP auth mode. Network-level restrictions should also be implemented using Kubernetes network policies or ingress controllers to restrict access to the Nuclio Dashboard service exclusively from trusted internal subnets and authorized administrative IPs. Additionally, implementing strict input validation for all handler specifications in custom extensions can help mitigate risks associated with parsing flaws if similar issues exist elsewhere in the codebase.