Cloudflare, a prominent cybersecurity vendor renowned for its web protection services, faces a security challenge that could expose its customers to unforeseen risks. 

A recent disclosure from Certitude highlights a vulnerability that could allow attackers to bypass certain protection mechanisms offered by Cloudflare, leaving customers susceptible to attacks that the platform is designed to prevent.

Vulnerability Overview:

In their official documentation, Cloudflare outlines various mechanisms to safeguard origin servers from malicious traffic. 

However, this disclosure has shed light on a crucial gap in protection that stems from a trust relationship between Cloudflare and its customers’ websites. 

Attackers who use their Cloudflare accounts to abuse this trust relationship can exploit this trust relationship, rendering configured security measures ineffective.

1. Authenticated Origin Pulls:

One of the mechanisms affected is “Authenticated Origin Pulls,” which is considered “very secure” by Cloudflare. This method relies on client SSL certificates to authenticate connections between Cloudflare’s reverse proxy servers and the origin server. 

The issue arises when customers opt for the convenience of using Cloudflare’s certificate. This choice allows any connection originating from Cloudflare, regardless of the tenant, to be accepted. 

Attackers can exploit this by setting up a custom domain, pointing it to the victim’s IP address, and then bypassing protection features configured by the victim.

2. Allowlist Cloudflare IP addresses:

Another mechanism, “Allowlist Cloudflare IP addresses,” is labeled as “moderately secure.” It relies on rejecting connections that don’t originate from Cloudflare’s IP address ranges. 

Similar to authenticated origin pulls, this mechanism has a vulnerability that allows all connections from Cloudflare, regardless of the tenant, to be permitted. 

Attackers can exploit this by directing their attacks through Cloudflare’s infrastructure while bypassing the victim’s protection features.

Cloudflare customers should consider these vulnerabilities seriously and review their protection strategies. 

For the “Allowlist Cloudflare IP addresses” mechanism, it’s recommended to use Cloudflare Aegis, which provides dedicated egress IP addresses instead of shared IP address ranges. Additionally, for “Authenticated Origin Pulls,” customers should opt for custom certificates to ensure better security.

Cloudflare has been made aware of these vulnerabilities, and it is hoped that they will implement protection mechanisms to mitigate these risks and provide clearer guidance to customers with weak configurations.

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