CVE-2021-41792 in alfresco-content-services
Summary
by MITRE • 10/21/2021
An issue was discovered in Hyland org.alfresco:alfresco-content-services through 6.2.2.18 and org.alfresco:alfresco-transform-services through 1.3. A crafted HTML file, once uploaded, could trigger an unexpected request by the transformation engine. The response to the request is not available to the attacker, i.e., this is blind SSRF.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 10/28/2021
The vulnerability CVE-2021-41792 represents a significant security flaw within the Alfresco Content Services platform that affects versions up to 6.2.2.18 and the Alfresco Transform Services up to version 1.3. This issue manifests as a blind server-side request forgery vulnerability that arises from improper handling of crafted HTML files during the content transformation process. The vulnerability specifically impacts the transformation engine's ability to properly validate and sanitize user-supplied content, creating an attack vector that can be exploited by malicious actors to initiate unauthorized requests from the server.
The technical nature of this vulnerability stems from the transformation engine's failure to properly validate external references within HTML content that users upload to the system. When a specially crafted HTML file is processed by the transformation services, the engine attempts to resolve external resources referenced within the document, such as external scripts, images, or other web resources. This behavior creates an opportunity for attackers to construct HTML content that will trigger the server to make outbound requests to predetermined targets, even though the attacker cannot directly observe the responses from these requests.
The blind nature of this SSRF vulnerability means that while attackers can initiate requests from the vulnerable server, they cannot directly capture or observe the responses from these requests, making detection and exploitation more challenging. However, this does not diminish the severity of the vulnerability, as the attacker can still potentially leverage this capability to perform reconnaissance, test internal network boundaries, or even chain this vulnerability with other exploits to achieve more significant impacts. The vulnerability operates at the application layer and specifically targets the transformation services component, which is designed to convert various document formats into different representations for web display or further processing.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable attackers to potentially map internal network structures, test for internal services, or even facilitate more sophisticated attacks such as internal port scanning or service enumeration. The vulnerability affects organizations using Alfresco Content Services in environments where the transformation engine processes untrusted content, which is common in collaborative document management systems where users upload various file types for processing and display. This creates a significant risk for enterprises that rely on Alfresco for document management and content processing, as the vulnerability could be exploited to gain insights into internal network configurations or potentially bypass security controls.
Organizations should implement immediate mitigations including restricting external resource access for the transformation services, implementing strict content validation and sanitization processes, and applying the latest security patches released by Alfresco. The vulnerability aligns with CWE-918, which describes server-side request forgery vulnerabilities, and could potentially be leveraged as part of broader attack chains that align with ATT&CK techniques such as T1071.004 for application layer protocol traffic and T1018 for remote system discovery. Organizations should also consider network-level controls to prevent outbound requests from the transformation services to external addresses, and implement monitoring for unusual outbound network activity that might indicate exploitation attempts.