A critical Server-Side Request Forgery vulnerability in BentoPDF allows unauthenticated remote attackers to bypass security boundaries and access internal network resources.

The vulnerability exists due to a race condition in the hostname validation logic within the cloudflare/cors-proxy-worker.js file, where the hostname is validated independently of the final DNS resolution. This allows an unauthenticated attacker to force the proxy to fetch data from internal or restricted network endpoints.

The ability to perform Server-Side Request Forgery allows an attacker to interact with internal services that are not exposed to the public internet, potentially leading to unauthorized data exfiltration or internal service disruption. With a CVSS score of 8.6, this flaw poses a high risk to organizational confidentiality and infrastructure integrity. Successful exploitation could grant an attacker access to sensitive internal metadata or administrative interfaces that lack secondary authentication.

Immediate Action: Upgrade to BentoPDF version 2.8.7 or later immediately to incorporate the corrected hostname validation logic.

Proactive Monitoring: Review proxy access logs for requests targeting internal IP addresses (e.g., 127.0.0.1, 10.0.0.0/8, 192.168.0.0/16) or unexpected domain names that do not align with intended proxy usage.

Compensating Controls: Ensure the PROXY_SECRET environment variable is configured to enforce signature checks, and deploy network-level egress filtering to restrict the proxy from initiating requests to internal network segments.

Public Exploit Available: No confirmed public exploit exists; however, per CISA's SSVC assessment, a proof-of-concept exists.

Given the high severity of this Server-Side Request Forgery vulnerability and the existence of a proof-of-concept, immediate remediation is required. Administrators should prioritize upgrading to version 2.8.7 across all self-hosted instances. If immediate patching is not feasible, restrict the proxy deployment environment to prevent network-level access to internal resources.