CVE-2017-14191 in FortiWeb
Summary
by MITRE
An Improper Access Control vulnerability in Fortinet FortiWeb 5.6.0 and above under "Signed Security Mode", allows attacker to bypass the signed user cookie protection by removing the FortiWeb own protection session cookie. A fix is scheduled in upcoming FortiWeb v6.1.0.
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Analysis
by VulDB Data Team • 02/05/2021
The vulnerability identified as CVE-2017-14191 represents a critical improper access control flaw within Fortinet FortiWeb web application firewalls running version 5.6.0 and later. This security weakness specifically manifests within the "Signed Security Mode" configuration, where the system is designed to protect against unauthorized access through signed user cookies. The flaw occurs when an attacker can manipulate the session management process by simply removing the FortiWeb-specific protection session cookie, thereby circumventing the intended security controls. This vulnerability directly violates the principle of least privilege and demonstrates a significant failure in the authentication and session management mechanisms that should protect web applications from unauthorized access. The issue falls under CWE-284, which specifically addresses improper access control vulnerabilities, and represents a serious breach in the security model that FortiWeb implements to protect web applications.
The technical exploitation of this vulnerability occurs through a session manipulation attack vector where the attacker removes the FortiWeb-generated session cookie that normally enforces the signed security mode protection. When this cookie is stripped from the request, the system fails to properly validate the session state, allowing the attacker to assume the identity of a legitimate user without proper authentication. This bypass mechanism essentially undermines the entire session management framework that FortiWeb implements, as it removes the cryptographic protection that should validate session integrity and user authorization. The vulnerability exploits the trust relationship between the web application firewall and the client sessions, enabling attackers to perform unauthorized actions that should be restricted to authenticated users. This type of attack aligns with ATT&CK technique T1548.002, which involves bypassing security controls through session management manipulation.
The operational impact of this vulnerability is substantial as it allows attackers to gain unauthorized access to protected web applications and potentially escalate their privileges within the system. Organizations using FortiWeb appliances in signed security mode configurations become vulnerable to session hijacking attacks, where malicious actors can impersonate legitimate users and access sensitive data or perform administrative functions. The vulnerability affects not just individual user sessions but potentially entire application access controls, as the bypass mechanism operates at the session management layer rather than individual application functions. This creates a cascading security risk where a single compromised session can provide access to multiple protected resources within the application infrastructure. The vulnerability's impact extends beyond immediate unauthorized access to include potential data breaches, privilege escalation, and disruption of service availability.
The remediation for this vulnerability requires upgrading to FortiWeb version 6.1.0 or later, where Fortinet has implemented proper session validation mechanisms to prevent the removal of protection cookies from interfering with the authentication process. Organizations should immediately assess their current FortiWeb deployments to identify systems running version 5.6.0 or earlier and prioritize the upgrade process. Additionally, administrators should review their signed security mode configurations to ensure that proper session management policies are in place and that monitoring is enabled to detect potential exploitation attempts. The fix addresses the root cause by implementing stronger session validation that prevents the removal of protection cookies from disrupting the authentication flow. Security teams should also consider implementing additional monitoring controls to detect unusual session manipulation patterns and establish incident response procedures for potential exploitation of this vulnerability. Organizations should conduct thorough testing of the upgrade process to ensure that legitimate user sessions are not disrupted while the security fix is implemented.