CVE-2016-4312 in Identity Server
Summary
by MITRE
XML external entity (XXE) vulnerability in the XACML flow feature in WSO2 Identity Server 5.1.0 before WSO2-CARBON-PATCH-4.4.0-0231 allows remote authenticated users with access to XACML features to read arbitrary files, cause a denial of service, conduct server-side request forgery (SSRF) attacks, or have unspecified other impact via a crafted XACML request to entitlement/eval-policy-submit.jsp. NOTE: this issue can be combined with CVE-2016-4311 to exploit the vulnerability without credentials.
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Analysis
by VulDB Data Team • 09/13/2024
The CVE-2016-4312 vulnerability represents a critical XML external entity processing flaw within the XACML flow feature of WSO2 Identity Server version 5.1.0. This vulnerability specifically affects the entitlement/eval-policy-submit.jsp endpoint, which processes XACML policy evaluation requests. The flaw stems from insufficient input validation and sanitization of XML content, allowing malicious actors to manipulate the XML parsing process through crafted requests that reference external entities. The vulnerability is classified under CWE-611 as improper restriction of XML external entity reference, which directly enables attackers to exploit the system's XML processor in ways that were not intended or secured against.
The technical exploitation of this vulnerability occurs when authenticated users with access to XACML features submit specially crafted XACML requests containing external entity references. These requests can trigger the XML parser to resolve external entities, potentially leading to file disclosure attacks where arbitrary files on the server filesystem can be read and exfiltrated. The vulnerability also enables server-side request forgery attacks, allowing attackers to make requests to internal services that would normally be restricted, and can cause denial of service conditions by consuming system resources through malformed entity references. The attack surface is particularly concerning because it can be combined with CVE-2016-4311, which removes the authentication requirement, enabling unauthenticated exploitation of the XXE vulnerability through the same endpoint.
The operational impact of this vulnerability extends beyond simple data theft, as it can facilitate comprehensive system reconnaissance and lateral movement within network environments. Attackers can leverage the file reading capability to access sensitive configuration files, credential stores, and other system files that may contain authentication tokens, database connection strings, or other valuable information. The server-side request forgery component allows attackers to probe internal networks and potentially compromise other systems that are not directly exposed to the internet. This vulnerability essentially provides attackers with a powerful tool for information gathering, system enumeration, and privilege escalation within the WSO2 Identity Server environment, making it particularly dangerous in enterprise settings where identity servers often serve as central authentication points.
Organizations should implement multiple layers of mitigation to address this vulnerability effectively. The primary remediation involves applying the vendor-provided patch WSO2-CARBON-PATCH-4.4.0-0231, which specifically addresses the XXE processing issues in the affected XACML flow feature. Additionally, administrators should implement strict XML input validation and sanitization policies, disabling external entity processing in all XML parsers used within the application. Network segmentation and access controls should be enforced to limit access to the entitlement/eval-policy-submit.jsp endpoint to only authorized users and systems. Security monitoring should be enhanced to detect unusual patterns in XML request processing and file access attempts. Organizations should also consider implementing web application firewalls with XXE detection capabilities and regularly review and audit XACML policies to ensure they do not introduce unnecessary processing capabilities that could be exploited. The vulnerability aligns with ATT&CK technique T1213.002 (External Remote Services) and T1078.004 (Valid Accounts) as it exploits legitimate authentication mechanisms to gain access to system resources and enables attackers to establish persistent access through credential compromise and service exploitation.