Researchers have identified security gaps in Cloudflare’s firewall and distributed denial-of-service (DDoS) attack prevention mechanisms that can be exploited by attackers.
Certitude researcher Stefan Proksch reported that attackers can abuse their Cloudflare accounts to bypass security controls and make the protection mechanisms ineffective. The issue arises from the shared infrastructure available to all Cloudflare tenants, making it easy for malicious actors to abuse the trust relationship between Cloudflare and customers’ websites. Attackers can send their malicious payload through Cloudflare and bypass protection features, posing a significant security risk.
Furthermore, the first problem arises from using a shared Cloudflare certificate for Authenticated Origin Pulls, allowing attackers to send malicious payloads through Cloudflare. Attackers can set up a custom domain with Cloudflare and point it to a victim’s IP address, then disable all protection features for that custom domain in their tenant, enabling them to tunnel their attacks through Cloudflare’s infrastructure and bypass the victim’s protection measures.
The second issue involves the abuse of allowlisting Cloudflare IP addresses, which restricts traffic to the origin server to Cloudflare IP addresses. Attackers can use this mechanism to transmit rogue inputs and target other users on the Cloudflare platform. In response to the findings, Cloudflare has updated its documentation to emphasize the need for custom certificates for Authenticated Origin Pulls and the importance of considering additional security measures for origin servers.
Additionally, these security gaps highlight the need for continuous vigilance and proactive security measures to protect against evolving cybersecurity threats. Cloudflare users should be aware of these vulnerabilities and take steps to enhance their security posture, especially when dealing with shared infrastructure and trust relationships in cloud services.