CVE-2026-30857: Tencent Weknora Auth Bypass Vulnerability

CVE-2026-30857 Overview

CVE-2026-30857 is a cross-tenant authorization bypass vulnerability in Tencent WeKnora, an LLM-powered framework designed for deep document understanding and semantic retrieval. Prior to version 0.3.0, the knowledge base copy endpoint fails to properly validate tenant ownership, allowing any authenticated user to clone another tenant's knowledge base into their own tenant by knowing or guessing the source knowledge base ID. This enables bulk data exfiltration of document and FAQ content across tenants.

Critical Impact

Authenticated attackers can exfiltrate sensitive document and FAQ content from other tenants' knowledge bases, compromising multi-tenant data isolation and confidentiality.

Affected Products

• Tencent WeKnora versions prior to 0.3.0

Discovery Timeline

• 2026-03-07 - CVE CVE-2026-30857 published to NVD
• 2026-03-09 - Last updated in NVD database

Technical Details for CVE-2026-30857

Vulnerability Analysis

This vulnerability represents a classic Insecure Direct Object Reference (IDOR) combined with broken access control in a multi-tenant SaaS environment. The knowledge base copy endpoint in WeKnora accepts a source knowledge base ID parameter but fails to verify that the requesting user has legitimate access to that knowledge base. This authorization flaw (CWE-639: Authorization Bypass Through User-Controlled Key) allows any authenticated user to reference and duplicate knowledge bases belonging to other tenants.

The attack complexity is considered high because successful exploitation requires the attacker to know or successfully guess valid knowledge base IDs from other tenants. However, if knowledge base IDs follow predictable patterns (sequential integers, timestamps, etc.), enumeration becomes trivial. The impact is confined to confidentiality since the attacker can only read and copy data, not modify or delete the original knowledge base.

Root Cause

The root cause is missing authorization checks in the knowledge base copy endpoint. The application verifies that the requesting user is authenticated but does not validate whether the authenticated user belongs to the same tenant as the source knowledge base. This violates the principle of least privilege and breaks multi-tenant data isolation guarantees.

Attack Vector

The attack is network-based and requires low-privilege authenticated access to the WeKnora platform. An attacker would:

1. Authenticate to the WeKnora application with valid credentials (their own tenant account)
2. Identify or enumerate knowledge base IDs belonging to other tenants
3. Send a copy/clone request to the knowledge base copy endpoint specifying a target knowledge base ID from another tenant
4. The system clones the entire knowledge base contents (documents, FAQs, embeddings) into the attacker's tenant
5. The attacker now has full access to the exfiltrated data within their own tenant

The vulnerability mechanism involves the copy endpoint accepting any valid knowledge base ID without validating tenant ownership. When a clone request is received, the application retrieves the source knowledge base data and creates a duplicate under the requesting user's tenant context. For detailed technical information, see the GitHub Security Advisory.

Detection Methods for CVE-2026-30857

Indicators of Compromise

• Unusual knowledge base copy/clone operations in audit logs, particularly targeting knowledge base IDs outside the requesting user's tenant
• Spike in data transfer or storage consumption in a single tenant account
• API requests to the copy endpoint with sequential or enumerated knowledge base ID patterns

Detection Strategies

• Implement audit logging for all knowledge base copy operations including source and destination tenant IDs
• Monitor for cross-tenant reference attempts in API request logs
• Alert on knowledge base copy requests where source tenant differs from the authenticated user's tenant

Monitoring Recommendations

• Enable detailed API access logging for the knowledge base management endpoints
• Review audit trails for bulk copy operations or repeated copy attempts from single users
• Implement rate limiting on the copy endpoint to slow enumeration attacks

How to Mitigate CVE-2026-30857

Immediate Actions Required

• Upgrade Tencent WeKnora to version 0.3.0 or later immediately
• Audit knowledge base copy operations in logs to identify potential past exploitation
• Review tenant knowledge bases for unexpected content that may indicate unauthorized copying

Patch Information

Tencent has released version 0.3.0 of WeKnora which addresses this authorization bypass vulnerability. The patch implements proper tenant-level authorization checks on the knowledge base copy endpoint, ensuring users can only clone knowledge bases within their own tenant. Organizations should upgrade to 0.3.0 or later as soon as possible. For additional details, refer to the GitHub Security Advisory.

Workarounds

• If immediate upgrade is not possible, consider disabling or restricting access to the knowledge base copy functionality at the network or application layer
• Implement additional access controls at the API gateway level to validate tenant context before forwarding copy requests
• Use network segmentation to limit which users can access the knowledge base management API endpoints

# Example: Restrict access to the copy endpoint via nginx until patched
location /api/knowledge-base/copy {
    # Block access to the vulnerable endpoint
    deny all;
    return 403;
}