CVE-2016-3033 in AppScan
Summary
by MITRE
IBM AppScan Source 8.7 through 9.0.3.3 allows remote authenticated users to read arbitrary files or cause a denial of service (memory consumption) via an XML document containing an external entity declaration in conjunction with an entity reference, related to an XML External Entity (XXE) issue.
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Analysis
by VulDB Data Team • 06/14/2019
The vulnerability identified as CVE-2016-3033 affects IBM AppScan Source versions 8.7 through 9.0.3.3 and represents a critical XML External Entity (XXE) flaw that enables remote authenticated attackers to exploit the application through carefully crafted XML documents. This vulnerability resides in the XML processing functionality of the security scanning tool, where improper handling of external entity declarations creates a pathway for unauthorized file access and system resource exhaustion. The issue stems from the application's insufficient validation of XML input, particularly when processing documents containing external entity references that point to local system resources.
The technical exploitation of this XXE vulnerability occurs when an authenticated user submits a malicious XML document that contains an external entity declaration followed by an entity reference. The vulnerability manifests through the application's XML parser which fails to properly sanitize or restrict access to external entities, allowing attackers to reference local files on the system hosting the AppScan Source application. This flaw can potentially lead to information disclosure, where attackers can read sensitive files such as configuration data, credentials, or system files that are accessible to the application's user context. Additionally, the vulnerability can be leveraged for denial of service attacks by crafting XML documents that cause excessive memory consumption through recursive entity references or by referencing large files that consume system resources.
From an operational impact perspective, this vulnerability poses significant risks to organizations relying on IBM AppScan Source for security testing and vulnerability assessment. The authenticated nature of the attack means that an attacker must first obtain valid credentials to exploit the vulnerability, but this still represents a substantial risk given that security scanning tools often run with elevated privileges or have access to sensitive system information. The potential for information disclosure could expose sensitive organizational data, while the denial of service component could disrupt security testing operations and compromise the availability of the security scanning infrastructure. This vulnerability directly relates to CWE-611, which describes improper restriction of XML external entity references, and aligns with ATT&CK technique T1213.002 for Data from Information Repositories, highlighting the potential for unauthorized data access through XML processing flaws.
Organizations should immediately implement mitigations including updating to the latest available versions of IBM AppScan Source where the XXE vulnerability has been patched, configuring the application to disable external entity processing in XML parsers, and implementing strict input validation for all XML content processed by the application. Network segmentation and access controls should be reinforced to limit the attack surface, while monitoring should be enhanced to detect anomalous XML processing activities. The vulnerability also underscores the importance of proper XML parser configuration and input sanitization practices, with recommendations to disable external entity resolution and parameter entity expansion in all XML processing components. Security teams should conduct thorough assessments of their AppScan Source deployments to identify and remediate any configurations that may expose the system to similar XXE attack vectors, while also implementing regular vulnerability scanning to detect potential XXE issues in other applications within the organization's attack surface.