Emmett Framework Denial-of-Service Vulnerability via Malformed Cookie Headers

A denial-of-service vulnerability has been identified in the Emmett framework, specifically in versions prior to 1.3.11. The issue arises in the 'cookies' property of 'emmett_core.http.wrappers.Request', where the framework fails to properly handle 'CookieError' exceptions caused by malformed Cookie headers. This oversight allows unauthenticated attackers to send malformed cookies that trigger HTTP 500 errors, disrupting normal service and degrading server performance.

Impact

Exploitation of this vulnerability leads to HTTP 500 errors, causing a denial-of-service condition where the server struggles to process requests normally. This can result in significant performance degradation and service disruption.

Reproduction

The vulnerability can be reproduced by sending HTTP requests with Cookie headers that include special characters, such as parentheses or curly braces. The server will respond with an internal error, and after several such requests, the server's response time will be noticeably delayed, indicating a degraded service state.

Remediation

Users can upgrade to Emmett framework version 1.3.11 or later, where this vulnerability has been fixed.