CVE-2018-11386 in Symfony
Summary
by MITRE
An issue was discovered in the HttpFoundation component in Symfony 2.7.x before 2.7.48, 2.8.x before 2.8.41, 3.3.x before 3.3.17, 3.4.x before 3.4.11, and 4.0.x before 4.0.11. The PDOSessionHandler class allows storing sessions on a PDO connection. Under some configurations and with a well-crafted payload, it was possible to do a denial of service on a Symfony application without too much resources.
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Analysis
by VulDB Data Team • 03/27/2023
The vulnerability identified as CVE-2018-11386 resides within the HttpFoundation component of the Symfony web application framework, specifically affecting versions prior to the mentioned secure releases. This issue manifests in the PDOSessionHandler class which is responsible for storing session data through PDO database connections. The flaw represents a denial of service vulnerability that can be exploited under certain environmental configurations, allowing attackers to disrupt application availability without requiring substantial computational resources. The vulnerability impacts multiple Symfony version branches including 2.7.x, 2.8.x, 3.3.x, 3.4.x, and 4.0.x, demonstrating the widespread nature of the issue across the framework's major releases.
The technical root cause of this vulnerability stems from insufficient input validation and sanitization within the session handling mechanism. When the PDOSessionHandler processes session data, it fails to properly validate or escape certain parameters that could be manipulated by an attacker. This weakness creates an opportunity for crafted payloads to be executed within the context of the database connection, potentially leading to resource exhaustion or query manipulation that disrupts normal application operation. The vulnerability operates at the intersection of improper input handling and database interaction, making it particularly dangerous in environments where session data is frequently stored in relational databases.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the overall stability and availability of Symfony applications. Attackers can leverage this weakness to consume excessive database resources, causing timeouts, connection exhaustion, or even complete application unavailability. The low resource requirement for exploitation makes this vulnerability particularly attractive to attackers seeking to perform denial of service attacks without significant computational overhead. This type of vulnerability directly impacts the availability aspect of the CIA triad and can be classified under CWE-129 as "Improper Validation of Array Index" or CWE-770 as "Allocation of Resources Without Limits or Throttling" depending on the specific exploitation method employed.
Organizations affected by this vulnerability should immediately implement mitigations including upgrading to the patched versions of Symfony components, which address the input validation issues within the PDOSessionHandler class. Additionally, implementing proper input sanitization measures, limiting database connection resources, and monitoring for unusual session handling patterns can help reduce the attack surface. The vulnerability aligns with ATT&CK technique T1499.004 for "Endpoint Denial of Service" and demonstrates how seemingly minor input validation flaws can lead to significant operational disruptions. Security teams should also consider implementing database query monitoring and resource limiting to prevent exploitation attempts from consuming excessive system resources. The incident highlights the importance of proper session management and database interaction validation in web application security frameworks.