CVE-2014-8875 in Adserver
Summary
by MITRE
The XML_RPC_cd function in lib/pear/XML/RPC.php in Revive Adserver before 3.0.6 allows remote attackers to cause a denial of service (CPU and memory consumption) via a crafted XML-RPC request, aka an XML Entity Expansion (XEE) attack.
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Analysis
by VulDB Data Team • 04/09/2022
The vulnerability identified as CVE-2014-8875 represents a critical denial of service flaw within the Revive Adserver platform, specifically affecting versions prior to 3.0.6. This issue manifests through the XML_RPC_cd function located in the lib/pear/XML/RPC.php file, which fails to properly validate incoming XML-RPC requests. The vulnerability enables remote attackers to exploit XML Entity Expansion (XEE) techniques that can consume excessive system resources, leading to complete service disruption. The attack vector involves crafting malicious XML-RPC requests that contain expanded entity references, causing the application to process these entities recursively and consume disproportionate amounts of CPU cycles and memory resources. This type of vulnerability falls under the category of CWE-400, which specifically addresses Uncontrolled Resource Consumption, and represents a classic example of how XML parsing vulnerabilities can be weaponized for denial of service attacks. The flaw demonstrates a fundamental weakness in the application's input validation mechanisms and its handling of XML data structures.
The technical implementation of this vulnerability exploits the inherent behavior of XML parsers that automatically expand entity references during parsing operations. When the XML_RPC_cd function processes a malformed XML-RPC request containing crafted entity expansions, it fails to implement proper limits on entity expansion depth or total size. This allows attackers to construct XML payloads that reference entities which themselves reference other entities, creating a cascade of expansions that can grow exponentially. The result is a rapid consumption of system resources as the parser attempts to resolve and expand each entity reference, leading to CPU saturation and memory exhaustion. This vulnerability specifically targets the XML-RPC processing component of Revive Adserver, which is commonly used for remote procedure calls and integration with external systems, making it a particularly dangerous flaw in environments where external communication is expected. The attack can be executed without authentication and requires minimal technical expertise, making it a significant threat to system availability and operational continuity.
The operational impact of CVE-2014-8875 extends beyond simple service disruption to potentially compromise the entire ad serving infrastructure. When exploited successfully, the vulnerability can cause complete system unresponsiveness, preventing legitimate users from accessing advertising services and potentially leading to revenue loss for organizations relying on the platform. The resource exhaustion can affect not only the specific application instance but also underlying system resources, potentially impacting other services running on the same infrastructure. Organizations using Revive Adserver in production environments face significant risk as this vulnerability can be exploited by automated scanning tools or malicious actors seeking to disrupt advertising operations. The vulnerability also represents a potential vector for more sophisticated attacks, as the resource exhaustion can be used as a precursor to other exploit techniques or as part of larger attack campaigns targeting advertising infrastructure. From a security perspective, this vulnerability highlights the importance of proper XML parsing configurations and input validation in web applications, particularly those handling external data inputs.
Mitigation strategies for CVE-2014-8875 focus primarily on updating to the patched version of Revive Adserver 3.0.6 or later, which implements proper XML entity handling and resource limits. System administrators should also implement input validation measures that restrict the size and complexity of XML-RPC requests, particularly when processing external inputs. Network-level protections can include rate limiting and connection throttling to prevent rapid exploitation attempts. The implementation of XML parser configurations that disable external entity resolution and set limits on entity expansion depth provides additional defense in depth. Organizations should also consider implementing monitoring and alerting systems to detect unusual CPU and memory consumption patterns that may indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers Network Denial of Service, and represents a common technique used by threat actors to disrupt services. Regular security assessments and vulnerability scanning should include checks for XML parsing vulnerabilities, as similar issues can exist in other components of the application stack. The vulnerability also emphasizes the need for comprehensive security training for developers on proper XML handling techniques and the importance of adhering to secure coding practices that prevent resource exhaustion attacks.