Exposure of Sensitive Information to an Unauthorized Actor
Symfony prior to 2.3.19, 2.4.x prior to 2.4.9, and 2.5.x prior to 2.5.4is vulnerable to an Information Exposure vulnerability that would allow an attacker to directly access ESI URLs if accessed behind a trusted proxy.
CWE-200 - Information Exposure
An information exposure vulnerability is categorized as an information flow (IF) weakness, which can potentially allow unauthorized access to otherwise classified information in the application, such as confidential personal information (demographics, financials, health records, etc.), business secrets, and the application's internal environment.