CVE-2018-1067 in Undertow
Summary
by MITRE
In Undertow before versions 7.1.2.CR1, 7.1.2.GA it was found that the fix for CVE-2016-4993 was incomplete and Undertow web server is vulnerable to the injection of arbitrary HTTP headers, and also response splitting, due to insufficient sanitization and validation of user input before the input is used as part of an HTTP header value.
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Analysis
by VulDB Data Team • 03/14/2023
The vulnerability described in CVE-2018-1067 represents a critical security flaw in the Undertow web server implementation that stems from an incomplete remediation of a previously identified issue. This vulnerability affects Undertow versions prior to 7.1.2.CR1 and 7.1.2.GA, demonstrating how inadequate patching can leave systems exposed to continued exploitation. The flaw specifically relates to insufficient sanitization and validation of user input that occurs before such input is incorporated into HTTP header values, creating a pathway for malicious actors to manipulate the server's response handling mechanisms.
The technical nature of this vulnerability aligns with CWE-1107, which addresses improper validation of HTTP headers in web applications. The incomplete fix for CVE-2016-4993 has left Undertow susceptible to arbitrary HTTP header injection attacks, where attackers can inject malicious headers into HTTP responses. This vulnerability enables response splitting attacks, a technique that allows attackers to inject additional HTTP responses or manipulate existing ones by inserting carriage return and line feed characters into header values. The flaw occurs because the web server fails to properly sanitize user-provided input before incorporating it into HTTP header fields, creating a direct injection vector that bypasses the intended security controls.
The operational impact of this vulnerability is significant as it can enable multiple attack vectors including cross-site scripting attacks, session hijacking, and cache poisoning. An attacker exploiting this vulnerability can manipulate HTTP headers to redirect users to malicious sites, inject malicious content into responses, or manipulate browser behavior through header injection. The response splitting capability allows for more sophisticated attacks where attackers can craft multiple HTTP responses within a single connection, potentially leading to data leakage or unauthorized access to protected resources. This vulnerability particularly affects web applications that rely on Undertow as their underlying web server implementation and could compromise the integrity of web communications.
Organizations should implement immediate mitigations including updating to Undertow versions 7.1.2.CR1 or later where the vulnerability has been properly addressed. The fix involves enhanced input validation and sanitization mechanisms that properly escape or reject potentially malicious characters from user input before they can be processed as HTTP header values. Additionally, implementing proper HTTP header validation at the application level and deploying web application firewalls can provide additional layers of protection. Security monitoring should focus on detecting unusual HTTP header patterns and potential injection attempts. The vulnerability also highlights the importance of thorough regression testing when applying security patches to ensure that previous fixes have been completely implemented and that no residual vulnerabilities remain. This case study demonstrates how incomplete security remediation can create persistent threats and emphasizes the need for comprehensive vulnerability management processes.