CVE-2023-4554 in AppBuilder
Summary
by MITRE • 01/29/2024
Improper Restriction of XML External Entity Reference vulnerability in OpenText AppBuilder on Windows, Linux allows Server Side Request Forgery, Probe System Files.
AppBuilder's XML processor is vulnerable to XML External Entity Processing (XXE), allowing an authenticated user to upload specially crafted XML files to induce server-side request forgery, disclose files local to the server that processes them.
This issue affects AppBuilder: from 21.2 before 23.2.
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Analysis
by VulDB Data Team • 02/21/2024
The vulnerability described in CVE-2023-4554 represents a critical security flaw in OpenText AppBuilder software that manifests as an improper restriction of XML External Entity references. This weakness specifically impacts both Windows and Linux deployments of the application builder platform, creating a significant attack surface for malicious actors who can leverage this vulnerability to execute server-side request forgery attacks and probe system files. The vulnerability stems from insufficient input validation within the XML processing component of AppBuilder, which fails to properly sanitize external entity references in XML documents submitted by authenticated users.
The technical implementation of this vulnerability allows an authenticated user to upload malicious XML files that contain external entity declarations pointing to local system resources or external network endpoints. When the server processes these XML files through its XML parser, it automatically resolves these external entities, leading to unintended server-side behavior. The XXE processing mechanism in AppBuilder does not adequately restrict or disable external entity resolution, enabling attackers to construct XML payloads that can access local files on the server filesystem or initiate outbound network requests to arbitrary destinations. This behavior aligns with CWE-611, which specifically addresses improper restriction of XML external entity references, and represents a classic example of how XML parsers can be exploited to bypass normal security controls.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables attackers to perform server-side request forgery attacks that can be used to probe internal network resources, exfiltrate sensitive data from local files, or even escalate privileges within the application environment. An authenticated user with access to upload functionality can leverage this vulnerability to gain unauthorized access to system files that would normally be protected by filesystem permissions, potentially exposing configuration files, database credentials, or other sensitive information stored locally on the server. The vulnerability affects all versions of AppBuilder from 21.2 through the 23.2 release, indicating a prolonged period during which organizations using this platform were exposed to potential exploitation, making it particularly concerning for enterprises maintaining legacy systems.
Organizations should implement immediate mitigations including disabling external entity resolution in XML parsers, implementing strict input validation for all XML uploads, and restricting file upload capabilities to only trusted users with appropriate authorization levels. The remediation strategy should involve updating to the latest available version of AppBuilder that addresses this vulnerability, as well as implementing network-level controls to prevent unauthorized outbound connections from the application servers. Security teams should also consider deploying web application firewalls that can detect and block suspicious XML content patterns, and conduct comprehensive security assessments of all XML processing components within the application stack. This vulnerability demonstrates the importance of proper XML security configuration and aligns with ATT&CK technique T1213.002, which covers data from information repositories, as attackers can leverage XXE vulnerabilities to extract sensitive data from local system files through server-side request forgery mechanisms.