Cloudflare Updates Firewall to Block Brotli Exploit
The security provider released two new detection rules to mitigate a vulnerability in Next.js image optimization.
Updated on Oct. 26, 2026 in Cybersecurity
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Cloudflare has deployed two new Web Application Firewall detection rules to help identify and mitigate traffic associated with the CVE-2026-111497 Brotli vulnerability. These updates specifically monitor requests targeting the Next.js image optimization endpoint.
Why it matters
This update provides an automated defense mechanism for users leveraging Next.js, addressing a specific security flaw that could be exploited through Brotli body encoding. By implementing these protections, the platform reduces the risk of malicious traffic reaching vulnerable infrastructure.
The update introduces two new WAF rules configured to inspect incoming traffic for Brotli encoding headers and specific endpoint access patterns. Both rules are currently enabled in Log mode by default to facilitate security monitoring.
The players
Cloudflare
A global cloud services provider that offers content delivery network services, DDoS mitigation, and internet security software.
Next.js
A widely used React framework that enables developers to build full-stack web applications with server-side rendering and static site generation.
The details
The newly released firewall rules target traffic that declares Brotli body encoding while attempting to access the image optimization endpoint within Next.js. By operating in Log mode, the system allows administrators to identify potentially malicious activity without automatically blocking legitimate traffic during the initial rollout.
Timeline
October 25, 2026: Cloudflare released the Web Application Firewall updates.
The Tech Race
The rapid deployment of these firewall rules reflects the ongoing arms race between infrastructure providers and cyber threats targeting framework-specific vulnerabilities. This move signals a shift toward proactive edge-level filtering to address flaws in popular development frameworks like Next.js.
Users currently running Next.js applications do not need to take immediate manual action as the new rules are deployed in Log mode by default. Developers should review their firewall logs to determine if any of their traffic triggers these new detections.
The takeaway
Security professionals should prioritize auditing their web application logs to see if these new rules identify suspicious traffic patterns. Implementing timely updates at the edge remains a vital practice for protecting application frameworks from evolving vulnerabilities.
Further reading
For more information on protecting your web infrastructure, visit the Cybersecurity section.
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