CVE-2016-9181 in perl-Image-Info
Summary
by MITRE
perl-Image-Info: When parsing an SVG file, external entity expansion (XXE) was not disabled. An attacker could craft an SVG file which, when processed by an application using perl-Image-Info, could cause denial of service or, potentially, information disclosure.
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Analysis
by VulDB Data Team • 09/17/2024
The vulnerability identified as CVE-2016-9181 affects the perl-Image-Info library, which is widely used for extracting metadata and information from various image formats including scalable vector graphics. This flaw represents a classic external entity expansion vulnerability that falls under the CWE-611 category of Improper Restriction of XML External Entity Reference. The vulnerability exists in the XML parsing mechanism of the library when processing SVG files, where the application fails to disable external entity expansion during XML document parsing.
When an application utilizing perl-Image-Info processes a maliciously crafted SVG file, the library's XML parser attempts to resolve external entities referenced within the document. This behavior creates multiple attack vectors as defined by the ATT&CK framework under T1212 - Exploitation for Credential Access and T1499 - Endpoint Denial of Service. The vulnerability can be exploited to trigger denial of service conditions by causing the application to consume excessive resources through recursive entity expansion, or potentially lead to information disclosure if the external entities reference local files that could be accessed by the parsing process.
The technical implementation of this vulnerability stems from the library's failure to properly configure XML parsers to restrict external entity resolution. In XML processing contexts, this typically involves setting parser options to disable loading of external DTDs and entities, which is a fundamental security practice recommended by the OWASP XML Security Guidelines. The impact of this vulnerability extends beyond simple denial of service as it can potentially allow attackers to perform server-side request forgery attacks or extract sensitive information from the server's file system if proper input validation and sanitization are not implemented.
Organizations using perl-Image-Info in their applications should immediately update to patched versions of the library to prevent exploitation. The mitigation strategy involves ensuring that all XML parsing operations disable external entity expansion and restrict access to local resources. Security controls should include input validation to prevent unexpected XML content from being processed, along with network segmentation to limit potential attack surface. This vulnerability highlights the critical importance of proper XML parser configuration and demonstrates how seemingly innocuous library functions can create significant security risks when not properly secured against XML-based attacks. The ATT&CK framework categorizes this as a vulnerability exploitation technique that can be leveraged for both reconnaissance and persistent access, making it a significant concern for enterprise security teams.