CVE-2023-4639 in Undertow
Summary
by MITRE • 11/17/2024
A flaw was found in Undertow, which incorrectly parses cookies with certain value-delimiting characters in incoming requests. This issue could allow an attacker to construct a cookie value to exfiltrate HttpOnly cookie values or spoof arbitrary additional cookie values, leading to unauthorized data access or modification. The main threat from this flaw impacts data confidentiality and integrity.
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Analysis
by VulDB Data Team • 11/17/2024
The vulnerability identified as CVE-2023-4639 resides within the Undertow web server implementation, specifically targeting how it processes cookie values in HTTP requests. This flaw represents a critical security weakness that stems from improper parsing of cookie data structures, particularly when certain delimiting characters are present within cookie values. The vulnerability manifests when Undertow encounters cookie values containing special characters that are typically used to separate cookie attributes or values, creating a parsing ambiguity that can be exploited by malicious actors.
The technical root cause of this vulnerability aligns with CWE-1295, which addresses improper handling of cookie values in web applications, and specifically relates to CWE-20, which covers insufficient input validation. When Undertow processes incoming HTTP requests containing cookies with problematic delimiting characters, the server's cookie parsing mechanism fails to properly distinguish between legitimate cookie data and attack payloads. This parsing error creates a condition where an attacker can craft malicious cookie values that appear to contain multiple cookie entries when processed by the vulnerable server, effectively bypassing normal cookie validation and isolation mechanisms.
The operational impact of CVE-2023-4639 extends beyond simple data access violations to encompass significant threats to both data confidentiality and integrity. Attackers can exploit this vulnerability to exfiltrate HttpOnly cookie values, which are typically protected from client-side JavaScript access and designed to prevent cross-site scripting attacks. The ability to extract these protected cookies undermines fundamental web security assumptions and can lead to session hijacking, unauthorized access to protected resources, and privilege escalation attacks. Additionally, the vulnerability enables cookie spoofing capabilities that allow attackers to inject arbitrary cookie values, potentially modifying application behavior and state management in ways that compromise system integrity.
From an adversarial perspective, this vulnerability maps directly to several ATT&CK techniques including T1566 for credential access through social engineering and T1190 for exploitation of vulnerabilities in web applications. The attack surface is particularly concerning for web applications that rely heavily on cookie-based authentication and session management, as the vulnerability can be exploited without requiring privileged access or complex attack chains. Security professionals should note that this issue affects the foundational HTTP request processing layer, making it potentially exploitable across a wide range of applications that utilize Undertow as their web server implementation.
Mitigation strategies for CVE-2023-4639 should prioritize immediate patching of affected Undertow versions, as this represents the most effective defense against exploitation. Organizations should also implement additional monitoring for unusual cookie patterns and malformed cookie values in their web application firewalls and intrusion detection systems. Network-level protections can include configuring web proxies to normalize cookie values before they reach vulnerable applications, while application-level defenses should focus on implementing robust cookie validation and sanitization routines. The remediation process must also include comprehensive security testing to verify that cookie handling logic properly validates all incoming cookie data, ensuring that delimiting characters are appropriately escaped or rejected during processing to prevent similar parsing vulnerabilities from emerging in other components of the web application stack.