CVE-2020-4640 in API Connect
Summary
by MITRE
Certain IBM API Connect 10.0.0.0 through 10.0.1.0 and 2018.4.1.0 through 2018.4.1.13 configurations can result in sensitive information in the URL fragment identifiers. This information can be cached in the intermediate nodes like proxy servers, cdn, logging platforms, etc. An attacker can make use of this information to perform attacks by impersonating a user. IBM X-Force ID: 185510.
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Analysis
by VulDB Data Team • 02/23/2021
The vulnerability identified as CVE-2020-4640 affects IBM API Connect versions 10.0.0.0 through 10.0.1.0 and 2018.4.1.0 through 2018.4.1.13, representing a critical information disclosure issue that exploits the improper handling of sensitive data within URL fragment identifiers. This flaw enables attackers to extract confidential information from the fragment portion of URLs, which are typically intended to be client-side only and should not be transmitted to servers. The vulnerability stems from the system's failure to properly sanitize or validate URL components, particularly those used in authentication flows where session tokens or user identifiers might be inadvertently exposed through fragment parameters.
The technical implementation of this vulnerability involves the insecure transmission of sensitive information through URL fragments, which are often cached and stored by intermediate network infrastructure components including proxy servers, content delivery networks, and logging platforms. These intermediate nodes typically do not strip or sanitize fragment identifiers from URLs, meaning that sensitive data contained within them becomes permanently stored in caches, logs, and monitoring systems. The fragment identifier portion of a URL begins with a hash symbol followed by data that is intended to be processed by client-side JavaScript, but in this case, the system fails to prevent sensitive information from being included in these fragments, creating a vector for data leakage. This behavior violates fundamental security principles of information flow control and demonstrates a weakness in the application's input validation and output encoding mechanisms.
The operational impact of this vulnerability extends beyond simple information disclosure to enable sophisticated impersonation attacks that can compromise user sessions and access controls. Attackers can leverage the cached sensitive information to reconstruct user sessions, impersonate legitimate users, and gain unauthorized access to protected resources within the API management environment. The vulnerability creates a persistent threat vector since the cached information remains available for extended periods, potentially allowing attackers to maintain access long after initial exploitation. This type of attack pattern aligns with techniques described in the ATT&CK framework under credential access and privilege escalation domains, where adversaries exploit insecure storage of authentication tokens and session identifiers to gain unauthorized system access. The vulnerability particularly affects environments where API Connect serves as a gateway for enterprise applications, making it a significant concern for organizations managing sensitive data flows.
Mitigation strategies for CVE-2020-4640 require immediate implementation of proper URL sanitization and validation controls within the API Connect configuration. Organizations should implement strict input validation to prevent sensitive information from being included in URL fragments, particularly during authentication and authorization flows. The system configuration must be updated to ensure that fragment identifiers are properly handled and that sensitive data is either removed from fragments or properly encoded before being included in URLs. Security controls should include the implementation of proper access controls and session management mechanisms that do not rely on fragment-based identifiers for authentication purposes. Additionally, network infrastructure components should be configured to properly handle and sanitize URL fragments, and organizations should implement monitoring to detect and prevent the inadvertent exposure of sensitive information through URL parameters. This vulnerability represents a classic example of improper data handling that aligns with CWE-20, which describes improper input validation, and requires comprehensive security remediation across both application and infrastructure layers to prevent exploitation.