CVE-2014-9708 in PAN-OS
Summary
by MITRE
Embedthis Appweb before 4.6.6 and 5.x before 5.2.1 allows remote attackers to cause a denial of service (NULL pointer dereference) via a Range header with an empty value, as demonstrated by "Range: x=,".
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Analysis
by VulDB Data Team • 09/26/2022
The vulnerability identified as CVE-2014-9708 represents a critical denial of service weakness in Embedthis Appweb web server software versions prior to 4.6.6 and 5.x versions before 5.2.1. This flaw manifests when the server processes HTTP requests containing specially crafted Range headers with empty values, specifically demonstrating the issue through the example "Range: x=,". The vulnerability stems from inadequate input validation within the web server's request parsing logic, where the application fails to properly handle malformed Range header parameters.
The technical implementation of this vulnerability involves a NULL pointer dereference condition that occurs during the processing of HTTP Range requests. When the web server encounters a Range header with an empty value such as "Range: x=,", the application attempts to dereference a null pointer in its internal parsing routines. This typically happens when the server's Range header parser does not properly validate the structure of the header content before attempting to process the range parameters. The parsing logic fails to account for empty or malformed range specifications, leading to a segmentation fault or similar memory access violation that terminates the web server process.
From an operational perspective, this vulnerability presents a significant risk to web server availability and system reliability. Remote attackers can exploit this weakness by simply sending a crafted HTTP request containing the malformed Range header, requiring no authentication or specialized privileges. The impact is immediate and severe, as the denial of service affects the entire web server instance, potentially disrupting all hosted services and applications. Organizations relying on Embedthis Appweb for web hosting, application deployment, or content delivery would face complete service interruption until the server is manually restarted or the vulnerability is patched.
The vulnerability aligns with CWE-476, which describes NULL pointer dereference conditions in software implementations. From an adversarial perspective, this weakness fits within the attack pattern category of resource exhaustion and service disruption as outlined in the MITRE ATT&CK framework under the T1499.004 technique for network denial of service. The attack vector is particularly concerning because it requires minimal effort from attackers while delivering maximum impact, making it a preferred target for automated exploitation tools and malicious actors seeking to disrupt web services.
Organizations should immediately implement mitigations including updating to the patched versions of Embedthis Appweb, specifically version 4.6.6 or later for the 4.x series and version 5.2.1 or later for the 5.x series. Additionally, network-level protections such as web application firewalls can be configured to detect and block requests containing malformed Range headers, providing an additional layer of defense. System administrators should also implement monitoring solutions to detect unusual patterns of service disruption that might indicate exploitation attempts. The vulnerability demonstrates the critical importance of proper input validation and error handling in web server implementations, particularly for HTTP header parsing functions that must gracefully handle malformed inputs without crashing the entire service.