CVE-2016-4993 in WildFly
Summary
by MITRE
CRLF injection vulnerability in the Undertow web server in WildFly 10.0.0, as usued in Red Hat JBoss Enterprise Application Platform (EAP) 7.x before 7.0.2, allows remote attackers to inject arbitrary HTTP headers and conduct HTTP response splitting attacks via unspecified vectors.
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Analysis
by VulDB Data Team • 09/21/2022
The CVE-2016-4993 vulnerability represents a critical CRLF injection flaw within the Undertow web server component that forms the foundation of Red Hat JBoss Enterprise Application Platform 7.x versions prior to 7.0.2. This vulnerability exists at the HTTP protocol level where carriage return line feed sequences can be injected into HTTP headers, creating a pathway for attackers to manipulate the server's response handling mechanisms. The flaw specifically impacts the server's ability to properly sanitize input data before incorporating it into HTTP response headers, allowing malicious actors to inject arbitrary header content that can be interpreted by downstream components.
The technical exploitation of this vulnerability stems from insufficient input validation and sanitization within Undertow's header processing routines. When user-supplied data containing CRLF sequences is processed and included in HTTP response headers without proper encoding or filtering, attackers can inject additional headers that will be interpreted by web browsers and proxy servers. This creates a condition where attackers can manipulate the HTTP response stream to inject malicious headers, potentially redirecting users to malicious sites, injecting content, or conducting session hijacking attacks. The vulnerability operates under CWE-113 which specifically addresses improper neutralization of CRLF sequences in HTTP headers, making it a direct implementation of this well-known weakness in web application security.
From an operational perspective, this vulnerability presents significant risks to organizations using affected JBoss EAP versions as it enables sophisticated attack vectors including HTTP response splitting, cache poisoning, and cross-site scripting attacks. Attackers can leverage this flaw to manipulate browser behavior by injecting malicious headers that cause unexpected redirects or content injection, potentially leading to credential theft, session manipulation, or the delivery of malicious payloads. The impact extends beyond simple header injection as the vulnerability can be combined with other techniques to create more complex attack scenarios, making it particularly dangerous in enterprise environments where JBoss EAP serves as a core application platform. The vulnerability aligns with ATT&CK technique T1190 which covers exploiting vulnerabilities in web applications, specifically targeting the manipulation of HTTP response handling.
Organizations should prioritize immediate patching of affected systems to remediate this vulnerability, as the attack surface remains significant even in isolated network environments. The recommended mitigation strategy includes upgrading to JBoss EAP 7.0.2 or later versions where the vulnerability has been addressed through enhanced input validation and header sanitization mechanisms. Additionally, implementing proper input filtering at the application level, deploying web application firewalls, and conducting regular security assessments of HTTP header processing components can help reduce the risk exposure. Network segmentation and monitoring for unusual HTTP header patterns can provide additional detection capabilities for potential exploitation attempts, while regular security training for development teams can help prevent similar vulnerabilities in custom application code that interfaces with the affected server components.