CVE-2015-8978 in Soap Lite
Summary
by MITRE
In Soap Lite (aka the SOAP::Lite extension for Perl) 1.14 and earlier, an example attack consists of defining 10 or more XML entities, each defined as consisting of 10 of the previous entity, with the document consisting of a single instance of the largest entity, which expands to one billion copies of the first entity. The amount of computer memory used for handling an external SOAP call would likely exceed that available to the process parsing the XML.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 11/04/2024
The vulnerability identified as CVE-2015-8978 represents a critical denial of service condition within the Soap Lite Perl extension, specifically affecting versions 1.14 and earlier. This flaw manifests through a sophisticated form of XML entity expansion that exploits the recursive nature of XML entities to consume excessive system resources. The vulnerability operates by leveraging the XML parsing mechanism's inability to properly limit the expansion of nested entities, creating a scenario where seemingly benign XML documents can trigger massive resource consumption. The attack vector involves crafting malicious XML payloads that define multiple XML entities in a recursive relationship, where each entity references the previous one in a cascading expansion pattern.
The technical implementation of this vulnerability follows a well-established pattern of resource exhaustion attacks that target XML parsers. When an attacker constructs an XML document containing 10 or more XML entities, each entity is defined to consist of 10 instances of the preceding entity, creating a geometric progression that results in exponential expansion. The final document contains only a single instance of the largest entity, but during parsing this entity expands recursively to generate one billion copies of the initial entity. This exponential growth occurs because XML parsers typically expand entities during the parsing phase without adequate safeguards against such recursive expansion patterns. The vulnerability is classified under CWE-400 as an Uncontrolled Resource Consumption vulnerability, specifically manifesting as a form of XML External Entity (XXE) processing that leads to denial of service conditions.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire system stability and availability. When a SOAP::Lite process attempts to parse a maliciously crafted XML document, the memory consumption grows exponentially beyond the available process memory limits, often causing the application to crash or become unresponsive. This type of attack can be particularly devastating in enterprise environments where SOAP services handle critical business transactions, as it can effectively shut down entire service endpoints and potentially impact other applications sharing the same system resources. The vulnerability affects the core XML parsing functionality of the extension, making it difficult to distinguish between legitimate and malicious requests without implementing proper parsing restrictions. The attack requires minimal sophistication from an attacker perspective, as it only requires knowledge of XML entity syntax and the ability to construct a specific document structure.
Mitigation strategies for CVE-2015-8978 should focus on implementing comprehensive XML parsing restrictions and resource limitations. Organizations should immediately upgrade to Soap Lite version 1.15 or later, which includes fixes for the entity expansion vulnerability. Additionally, implementing XML parser configuration settings that limit the maximum number of entity expansions and the overall size of parsed documents provides an additional layer of protection. Network-level controls such as XML firewalls or API gateways can also be deployed to filter and validate incoming SOAP requests before they reach the vulnerable application. The implementation of input validation and sanitization routines that monitor for suspicious entity expansion patterns represents another effective mitigation approach. From an ATT&CK framework perspective, this vulnerability aligns with techniques targeting resource exhaustion and application-level attacks, specifically mapping to T1499.004 for Network Denial of Service and T1211 for Exploitation for Privilege Escalation. Organizations should also consider implementing monitoring and alerting mechanisms to detect unusual memory consumption patterns that might indicate exploitation attempts.