CVE-2017-9785 in Nancy
Summary
by MITRE
Csrf.cs in NancyFX Nancy before 1.4.4 and 2.x before 2.0-dangermouse has Remote Code Execution via Deserialization of JSON data in a CSRF Cookie.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 12/13/2022
The vulnerability identified as CVE-2017-9785 affects the NancyFX web framework, specifically targeting versions prior to 1.4.4 and 2.x versions before 2.0-dangermouse. This represents a critical security flaw that combines cross-site request forgery protection mechanisms with dangerous deserialization practices, creating a pathway for remote code execution. The issue resides in the Csrf.cs file which handles CSRF cookie management and processing within the Nancy framework's security architecture.
The technical flaw stems from the framework's handling of JSON data within CSRF cookies, where the application fails to properly validate or sanitize serialized objects before deserializing them. When an attacker crafts a malicious JSON payload and places it within a CSRF cookie, the framework's deserialization process executes arbitrary code on the server. This vulnerability operates at the intersection of insecure deserialization patterns and inadequate input validation, allowing attackers to bypass normal security controls and execute arbitrary commands with the privileges of the web application. The flaw essentially transforms a security mechanism designed to prevent CSRF attacks into a vector for remote code execution.
The operational impact of this vulnerability is severe and far-reaching for any organization using affected versions of NancyFX. Attackers can leverage this weakness to gain complete control over affected web applications, potentially leading to data breaches, system compromise, and full network infiltration. The vulnerability affects the core security infrastructure of the framework, meaning that any application relying on NancyFX for web services becomes vulnerable to remote code execution attacks. This creates a significant risk for organizations where web applications are exposed to untrusted networks or where the framework handles sensitive data processing. The exploitability of this vulnerability is particularly concerning because it requires minimal privileges to execute and can be delivered through standard web traffic.
Mitigation strategies for this vulnerability should prioritize immediate patching of all affected NancyFX versions to the latest secure releases. Organizations must implement comprehensive monitoring of their web application traffic to detect potential exploitation attempts and ensure proper input validation is in place for all cookie handling mechanisms. The security community has classified this vulnerability under CWE-502, which specifically addresses deserialization of untrusted data, and it aligns with ATT&CK technique T1203, which covers exploitation of remote services. Additionally, implementing proper application firewalls, input sanitization, and regular security assessments can help reduce the attack surface and provide defense-in-depth measures against similar vulnerabilities in the future.