CVE-2016-1343 in Information Server
Summary
by MITRE
The XML parser in Cisco Information Server (CIS) 6.2 allows remote attackers to read arbitrary files or cause a denial of service (CPU and memory consumption) via an external entity declaration in conjunction with an entity reference, related to an XML External Entity (XXE) issue, aka Bug ID CSCuy39059.
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Analysis
by VulDB Data Team • 11/04/2018
The vulnerability identified as CVE-2016-1343 represents a critical XML External Entity (XXE) flaw within Cisco Information Server version 6.2, classified under CWE-611. This vulnerability arises from the improper handling of XML input by the CIS XML parser, which fails to adequately validate or restrict external entity declarations. The flaw enables malicious actors to exploit the system through carefully crafted XML documents that contain external entity references, creating a pathway for unauthorized access to system resources and potential system compromise.
The technical implementation of this vulnerability occurs when the XML parser processes documents containing external entity declarations that reference local files or network resources. Attackers can construct malicious XML payloads that include entity references pointing to sensitive system files such as configuration files, credential stores, or system directories. When the parser resolves these entities, it can inadvertently read and expose the contents of these files to the attacker, potentially leading to information disclosure of sensitive data. The vulnerability also permits denial of service attacks through memory exhaustion or CPU consumption by crafting XML documents with recursive entity references or large external entities that cause the parser to consume excessive system resources.
The operational impact of this vulnerability extends beyond simple information disclosure to encompass potential system compromise and service disruption. Remote attackers can leverage this XXE vulnerability to perform server-side request forgery attacks, potentially accessing internal network resources that would normally be protected by firewalls or network segmentation. The denial of service capabilities can be particularly damaging in production environments where CIS serves as a critical data processing component, as sustained resource exhaustion attacks could render the system unavailable to legitimate users. This vulnerability affects the core functionality of the information server and can be exploited without authentication, making it particularly dangerous in environments where the system is exposed to untrusted input sources.
Security mitigations for this vulnerability should focus on implementing strict XML parser configuration and input validation measures. Organizations should disable external entity resolution in XML parsers and restrict access to local resources through proper firewall rules and network segmentation. The implementation of XML schema validation and input sanitization techniques can prevent malformed XML from being processed by the system. Additionally, regular updates and patches should be applied to ensure that the CIS software remains protected against known vulnerabilities. Network monitoring should be enhanced to detect suspicious XML processing activities, and access controls should be implemented to limit the sources from which XML data can be submitted to the system. This vulnerability aligns with ATT&CK technique T1213.002 for data from information repositories and T1499.004 for network disruption, highlighting the dual nature of the threat as both information disclosure and denial of service vector.