CVE-2026-21759: HCL Hive Information Disclosure Vulnerability

CVE-2026-21759 Overview

CVE-2026-21759 is an information exposure vulnerability affecting HCL Hive. The application exposes its Swagger API documentation to unauthenticated users over the network. HCL confirmed that no sensitive information such as credentials or personally identifiable information (PII) was included in the exposed documentation. However, publishing API schemas, endpoints, and parameter definitions to anonymous users expands the reconnaissance surface available to attackers. The weakness is tracked as [CWE-215: Insertion of Sensitive Information Into Debugging Code].

Critical Impact
Unauthenticated network users can enumerate HCL Hive API endpoints and parameters through publicly exposed Swagger documentation, aiding targeted follow-on attacks.

Affected Products

HCL Hive (specific version ranges not published in NVD entry)

Discovery Timeline

2026-08-24 - CVE-2026-21759 published to NVD
2026-08-24 - Last updated in NVD database

Technical Details for CVE-2026-21759

Vulnerability Analysis

HCL Hive serves its Swagger (OpenAPI) documentation on a network-reachable endpoint without requiring authentication. Swagger interfaces describe every exposed REST route, HTTP method, request body schema, response schema, and often internal parameter names. When served to anonymous users, this documentation acts as a map of the application's attack surface.

The vendor investigation confirmed that no credentials, tokens, or PII were embedded in the exposed pages. The vulnerability is therefore limited to disclosure of API design information rather than direct data leakage. Attackers commonly use such documentation to identify undocumented parameters, deprecated routes, and administrative endpoints that can be probed for further weaknesses such as broken access control or injection flaws.

EPSS data lists the exploit probability at 0.222% with a percentile of 12.598, reflecting low near-term exploitation likelihood.

Root Cause

The root cause is a missing authorization control on the route that renders Swagger UI and the underlying OpenAPI specification. API documentation generators are frequently mounted for development convenience and left reachable in production builds without an authentication middleware in front of them.

Attack Vector

An unauthenticated remote attacker requests the Swagger documentation URL over the network. Successful retrieval requires user interaction only in the sense of navigating to the endpoint. The attacker then parses the OpenAPI document to enumerate routes, request schemas, and undocumented behavior for use in reconnaissance and later exploitation attempts.

No verified public proof-of-concept code or exploit is available. Refer to the HCL Software Knowledge Base Article for vendor guidance.

Detection Methods for CVE-2026-21759

Indicators of Compromise

Anonymous HTTP GET requests to Swagger UI paths such as /swagger, /swagger-ui, /swagger-ui.html, /api-docs, or /v3/api-docs on HCL Hive hosts.
Repeated crawling of documented API endpoints from a single external source shortly after Swagger retrieval.
Web server access logs showing enumeration of endpoints named in the OpenAPI specification.

Detection Strategies

Query web access logs for unauthenticated requests to documentation routes and correlate with the client IP's subsequent API calls.
Deploy a web application firewall (WAF) rule that alerts when Swagger paths return HTTP 200 to unauthenticated sessions.
Compare the list of endpoints requested by external clients against endpoints defined in the exposed OpenAPI file.

Monitoring Recommendations

Baseline expected consumers of the HCL Hive API and alert on new source addresses issuing schema requests.
Monitor for spikes in HTTP 401 and 403 responses that follow a Swagger retrieval event, which indicates active enumeration.
Forward HCL Hive access logs to a centralized analytics platform for retention and correlation with other reconnaissance signals.

How to Mitigate CVE-2026-21759

Immediate Actions Required

Apply the remediation guidance published in the HCL Software Knowledge Base Article.
Restrict access to Swagger and OpenAPI endpoints so they are reachable only from authenticated administrative sessions or trusted internal networks.
Review web server, reverse proxy, and API gateway configurations for exposed documentation routes across all HCL Hive instances.

Patch Information

HCL has issued guidance through knowledge base article KB0131731. Administrators should follow the vendor advisory to apply the fix or configuration change that removes public access to the Swagger documentation endpoint. Confirm the change by requesting the documentation URL from an unauthenticated external host and verifying that the response is 401, 403, or 404.

Workarounds

Add an authentication middleware or reverse proxy rule in front of /swagger* and /api-docs* routes to require valid credentials.
Disable Swagger generation entirely in production builds and enable it only in non-production environments.
Block external access to documentation paths at the network edge using WAF or firewall rules until the vendor fix is applied.

bash

# Configuration example: NGINX rule to restrict Swagger endpoints to an internal CIDR
location ~ ^/(swagger|swagger-ui|api-docs|v3/api-docs) {
    allow 10.0.0.0/8;
    deny all;
    proxy_pass http://hcl_hive_backend;
}