CVE-2021-32812 in Monkshu
Summary
by MITRE • 08/03/2021
Monkshu is an enterprise application server for mobile apps (iOS and Android), responsive HTML 5 apps, and JSON API services. In version 2.90 and earlier, there is a reflected cross-site scripting vulnerability in frontend HTTP server. The attacker can send in a carefully crafted URL along with a known bug in the server which will cause a 500 error, and the response will then embed the URL provided by the hacker. The impact is moderate as the hacker must also be able to craft an HTTP request which should cause a 500 server error. None such requests are known as this point. The issue is patched in version 2.95. As a workaround, one may use a disk caching plugin.
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Analysis
by VulDB Data Team • 08/07/2021
The vulnerability identified as CVE-2021-32812 affects Monkshu, an enterprise application server designed to support mobile applications across iOS and Android platforms, responsive HTML5 applications, and JSON API services. This cross-site scripting flaw exists within the frontend HTTP server component of the software, specifically in versions 2.90 and earlier. The vulnerability manifests when malicious actors exploit a reflected XSS vector through carefully crafted URLs that trigger server-side errors, creating conditions that allow for code injection attacks against unsuspecting users.
The technical implementation of this vulnerability involves a specific interaction between client-side request manipulation and server-side error handling mechanisms. When an attacker crafts a malicious URL and submits it to the vulnerable system, the server processes this request and generates a 500 internal server error response. During this error handling process, the server inadvertently embeds the malicious URL content within the error response, creating a reflected cross-site scripting condition. This behavior follows the CWE-79 pattern of cross-site scripting where untrusted data flows from the web server to the user's browser without proper sanitization or encoding. The vulnerability requires specific conditions to be exploited, as noted in the advisory, since attackers must first identify a request pattern that triggers the 500 error response, which is not currently documented in known attack vectors.
The operational impact of this vulnerability is classified as moderate, reflecting the specific prerequisites required for exploitation. While the vulnerability exists in the software, the attack vector requires both the ability to craft malicious HTTP requests that cause server errors and the specific error handling behavior that leads to code injection. This limitation reduces the overall risk compared to more direct XSS vulnerabilities, but still presents a legitimate security concern for organizations using affected versions of the Monkshu platform. The vulnerability affects the integrity of web application responses and could potentially allow attackers to execute malicious scripts in the context of a victim's browser session, potentially leading to session hijacking, data theft, or other malicious activities.
The remediation for this vulnerability involves upgrading to version 2.95 of the Monkshu application server, which includes patches addressing the reflected XSS conditions in the frontend HTTP server. Organizations should implement this update as a priority to eliminate the risk of exploitation. As a temporary mitigation measure, administrators can deploy a disk caching plugin as a workaround to reduce the exposure window while planning the full upgrade. This approach follows the principle of defense in depth and aligns with security best practices for managing vulnerabilities. The ATT&CK framework would categorize this vulnerability under the T1212 technique of Exploitation for Credential Access, as reflected XSS vulnerabilities can be leveraged to steal session cookies or perform actions on behalf of authenticated users. Organizations should also consider implementing web application firewalls and input validation controls to further protect against similar vulnerabilities in their application environments.