CVE-2020-4706 in API Connect
Summary
by MITRE • 08/17/2021
IBM API Connect 5.0.0.0 through 5.0.8.10 is vulnerable to HTTP header injection, caused by improper validation of input by the HOST headers. By sending a specially crafted HTTP request, a remote attacker could exploit this vulnerability to inject HTTP HOST header, which will allow the attacker to conduct various attacks against the vulnerable system, including cross-site scripting, cache poisoning or session hijacking. IBM X-Force ID: 187194.
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Analysis
by VulDB Data Team • 08/19/2021
IBM API Connect versions 5.0.0.0 through 5.0.8.10 contain a critical HTTP header injection vulnerability that stems from inadequate input validation mechanisms within the HOST header processing functionality. This flaw resides in the application layer of the web server stack and represents a direct violation of secure coding principles that mandate proper sanitization and validation of all external inputs. The vulnerability manifests when the system fails to adequately filter or escape special characters within the HOST header, allowing malicious actors to inject arbitrary HTTP headers that can be interpreted by the application server. This weakness aligns with CWE-113, which specifically addresses improper neutralization of characters or elements within HTTP headers, and constitutes a fundamental breakdown in the application's defense-in-depth strategy.
The operational impact of this vulnerability extends far beyond simple header injection, creating a gateway for sophisticated attack vectors that can compromise the entire API management infrastructure. A remote attacker exploiting this weakness can manipulate the HOST header to inject malicious content that may be processed by downstream applications, enabling cross-site scripting attacks that can execute arbitrary JavaScript within the victim's browser context. Additionally, the vulnerability facilitates cache poisoning attacks where malicious content is injected into server caches, potentially affecting multiple users and sessions. Session hijacking becomes possible as attackers can manipulate session identifiers or authentication tokens through header manipulation, allowing unauthorized access to protected resources. The attack surface is further expanded through the potential for man-in-the-middle scenarios where attackers can redirect traffic or modify responses based on the injected headers.
This vulnerability directly maps to several techniques documented in the MITRE ATT&CK framework, particularly under the T1190 category for Proxy Execution and T1059 for Command and Scripting Interpreter, as the injection capabilities can be leveraged to execute malicious commands or scripts within the API management environment. The attack chain typically begins with reconnaissance to identify the vulnerable IBM API Connect instances, followed by crafting of malicious HTTP requests containing specially formatted HOST headers that bypass input validation. The exploitation process often involves encoding techniques such as URL encoding or line break injection to circumvent basic validation checks that may be in place. Organizations running these vulnerable versions face significant risk of data breaches, service disruption, and potential lateral movement within their network infrastructure, as the API gateway serves as a critical entry point for numerous applications and services.
Mitigation strategies should prioritize immediate patching of affected IBM API Connect instances to the latest supported versions that contain proper input validation fixes. Network segmentation and monitoring solutions should be deployed to detect anomalous HTTP header patterns that may indicate exploitation attempts, with specific attention to unusual line break sequences or encoded characters within HOST headers. Implementing strict input validation rules that enforce RFC-compliant header formats, along with regular security assessments and penetration testing, can help identify similar vulnerabilities in related systems. Organizations should also consider deploying web application firewalls that can detect and block malicious header injection attempts, while establishing comprehensive logging and alerting mechanisms to monitor for suspicious header manipulation activities. The remediation process must include thorough testing to ensure that the applied patches do not introduce regressions in legitimate API functionality, as the API gateway serves critical business operations within enterprise environments.