An unauthenticated server-side request forgery vulnerability in Bisheng allows remote attackers to probe internal network infrastructure and access sensitive cloud metadata.

The vulnerability exists in the POST /api/v1/workflow/report/callback endpoint, which fails to implement authentication, URL scheme restrictions, or host filtering. This allows an unauthenticated attacker to force the application to perform arbitrary HTTP requests to internal resources.

Successful exploitation of this flaw can lead to the exposure of sensitive internal network topology and cloud service metadata, which are often used to facilitate further attacks. Given the CVSS score of 8.2, this high-severity vulnerability poses a significant risk to the confidentiality of internal systems and data stored in connected object storage, potentially enabling unauthorized retrieval of sensitive documents.

Immediate Action: Update the Bisheng deployment to a version beyond 2.6.0-fix2 as soon as the vendor provides a patch.

Proactive Monitoring: Monitor server access logs for unusual outbound requests originating from the Bisheng backend, specifically targeting internal IP ranges or cloud metadata service addresses (e.g., 169.254.169.254).

Compensating Controls: Implement strict egress filtering on the network hosting the Bisheng instance to prevent the server from initiating connections to unauthorized internal or private network segments.

Public Exploit Available: Unknown

The absence of authentication on the workflow callback endpoint represents a critical oversight that requires immediate attention. Organizations utilizing Bisheng should verify their current version and prioritize the application of security updates to prevent unauthorized internal reconnaissance. If an immediate update is not feasible, implement robust network-level egress controls to restrict the ability of the Bisheng service to communicate with non-public infrastructure.