The ewe web server contains a critical denial of service vulnerability in its header parsing logic that can be triggered by any unauthenticated remote attacker to crash the application process.

This vulnerability is caused by a logic error in the handle_trailers function, where rejected trailer headers trigger recursive calls without advancing the buffer. This flaw allows an unauthenticated remote client to force the BEAM process into an infinite loop, resulting in permanent 100% CPU utilization.

Successful exploitation of this vulnerability results in a complete denial of service for any application utilizing the ewe server. Because the flaw is exploitable by unauthenticated remote users and occurs before application code execution, it presents a high risk to availability. With a CVSS score of 7.5, this high-severity issue necessitates immediate remediation to prevent service outages and potential operational disruption.

Immediate Action: Update the ewe dependency to version 3.0.5 or later as specified in the Hex package manager.

Proactive Monitoring: Monitor server CPU utilization metrics for sudden, sustained spikes to 100% and review web server access logs for malformed or unusual chunked request headers.

Compensating Controls: Implement a Web Application Firewall (WAF) or load balancer configured to inspect and filter suspicious chunked transfer-encoding requests before they reach the web server.

Public Exploit Available: Unknown.

Given the ease of exploitation and the severe impact on system availability, administrators must prioritize updating the ewe library to version 3.0.5 immediately. Relying on application-level workarounds is ineffective, as the vulnerability is triggered before application logic is reached, making patching the only reliable method to mitigate this risk.