CVE-2002-2428 in WebServer
Summary
by MITRE
webs.c in GoAhead WebServer before 2.1.4 allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via an HTTP POST request that contains a Content-Length header but no body data.
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Analysis
by VulDB Data Team • 10/27/2018
The vulnerability identified as CVE-2002-2428 affects the GoAhead WebServer version 2.1.3 and earlier, representing a critical denial of service flaw that can be exploited by remote attackers to crash the web server daemon. This vulnerability resides within the webs.c component of the web server software, which handles HTTP request processing and response generation. The flaw specifically manifests when the web server receives an HTTP POST request that includes a Content-Length header but contains no actual request body data, creating a condition that leads to a NULL pointer dereference during request handling.
The technical mechanism behind this vulnerability stems from inadequate input validation within the web server's HTTP request parsing logic. When the GoAhead WebServer processes an HTTP POST request with a Content-Length header but no accompanying request body, the software fails to properly validate the presence of actual data before attempting to access memory locations that would normally contain the request body content. This results in a NULL pointer dereference error, which causes the web server daemon to terminate abruptly and crash. The vulnerability is classified under CWE-476 as a NULL pointer dereference, which represents a common programming error where a program attempts to access memory through a pointer that has not been properly initialized or validated.
From an operational perspective, this vulnerability poses significant risks to web server availability and system reliability. Remote attackers can exploit this flaw by simply sending a crafted HTTP POST request with a Content-Length header but empty body data, requiring no authentication or special privileges. The impact of such an attack extends beyond simple service disruption, as it can lead to complete web server unavailability, potentially affecting business operations and user access to web applications. The vulnerability is particularly concerning because it can be exploited from any remote location without requiring any specific authentication credentials, making it an attractive target for automated attacks and denial of service campaigns.
The exploitation of this vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks. Attackers can leverage this weakness to perform sustained denial of service attacks against web servers, potentially causing service outages that could impact business continuity and customer access to online services. The vulnerability demonstrates poor defensive programming practices and highlights the importance of input validation and proper error handling in web server implementations. Organizations running affected versions of GoAhead WebServer are particularly vulnerable to this type of attack, as the flaw exists in the core request processing functionality that handles all HTTP POST requests regardless of their legitimacy or intended use.
Mitigation strategies for this vulnerability include immediate patching of the GoAhead WebServer to version 2.1.4 or later, which contains the necessary fixes to properly handle HTTP POST requests with Content-Length headers but empty body data. System administrators should also implement network-level protections such as firewall rules that can detect and block suspicious HTTP POST requests, though these measures may not prevent all instances of exploitation. Additionally, deploying intrusion detection systems that can identify patterns associated with this specific vulnerability can provide early warning of potential attacks. Organizations should also consider implementing web application firewalls and monitoring systems that can detect anomalous HTTP request patterns that might indicate exploitation attempts. The fix implemented in version 2.1.4 addresses the core issue by ensuring proper validation of HTTP request bodies before attempting to access memory locations, thereby preventing the NULL pointer dereference condition that led to the daemon crash.