CVE-2019-5442 in Pippo
Summary
by MITRE
XML Entity Expansion (Billion Laughs Attack) on Pippo 1.12.0 results in Denial of Service.Entities are created recursively and large amounts of heap memory is taken. Eventually, the JVM process will run out of memory. Otherwise, if the OS does not bound the memory on that process, memory will continue to be exhausted and will affect other processes on the system.
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Analysis
by VulDB Data Team • 10/05/2023
The vulnerability identified as CVE-2019-5442 represents a critical XML entity expansion flaw affecting Pippo 1.12.0, specifically exposing systems to the well-known Billion Laughs attack pattern. This vulnerability stems from inadequate input validation within the XML processing mechanism, allowing malicious actors to craft specially formatted XML documents that trigger recursive entity expansion. The attack exploits the fundamental behavior of XML parsers that resolve entity references, creating a cascading effect where each entity reference can expand into multiple entities, leading to exponential growth in the parsed document size.
The technical implementation of this vulnerability occurs when the XML parser encounters entity declarations that reference other entities in a recursive manner. In the Billion Laughs attack pattern, an attacker creates a series of entity definitions where each entity references multiple instances of other entities, ultimately resulting in the parser consuming enormous amounts of memory during the expansion process. The vulnerability manifests as a denial of service condition where the Java Virtual Machine process gradually consumes all available heap memory, eventually leading to OutOfMemoryError exceptions and complete system unresponsiveness.
The operational impact of this vulnerability extends beyond simple service disruption, creating cascading effects that can compromise entire system stability. When the JVM process exhausts its allocated heap memory, it becomes unresponsive and may crash entirely, requiring manual intervention for restart. In environments where memory constraints are not properly enforced at the operating system level, the memory exhaustion can spill over to affect other critical processes running on the same system. This creates a significant risk for production environments where multiple services share system resources, potentially leading to widespread service degradation or complete system failure.
Security professionals should recognize this vulnerability as a variant of CWE-400, specifically related to insufficient input validation and resource exhaustion in XML processing. The attack pattern aligns with techniques documented in the MITRE ATT&CK framework under the T1499.004 subtechnique for Network Denial of Service, where adversaries leverage application-level vulnerabilities to exhaust system resources. Organizations should implement immediate mitigations including XML parser configuration changes that limit entity expansion, enforce strict memory limits on JVM processes, and deploy input validation mechanisms that prevent recursive entity references. The recommended approach involves updating to Pippo version 1.12.1 or later, which includes proper safeguards against recursive entity expansion, combined with network-level filtering and monitoring to detect suspicious XML processing patterns.