CVE-2021-38677 in QcalAgent
Summary
by MITRE • 01/14/2022
A cross-site scripting (XSS) vulnerability has been reported to affect QNAP device running QcalAgent. If exploited, this vulnerability allows remote attackers to inject malicious code. We have already fixed this vulnerability in the following versions of QcalAgent: QcalAgent 1.1.7 and later
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Analysis
by VulDB Data Team • 01/17/2022
The CVE-2021-38677 vulnerability represents a critical cross-site scripting flaw within QNAP devices that utilize the QcalAgent component. This vulnerability exposes QNAP NAS systems to potential remote code execution risks through malicious web-based attacks targeting the device's web interface. The flaw specifically resides in how QcalAgent processes user input within its web application framework, creating an attack vector that allows remote adversaries to inject malicious scripts into web pages viewed by other users. This type of vulnerability falls under CWE-79 which categorizes improper neutralization of input during web page generation, making it a classic example of client-side script injection that can compromise user sessions and potentially lead to full system compromise.
The technical exploitation of this vulnerability occurs when attackers craft malicious payloads that are executed within the context of a victim's browser session interacting with the vulnerable QNAP device. The attack typically involves injecting malicious JavaScript code through input fields or parameters that are not properly sanitized before being rendered in web responses. This allows attackers to execute arbitrary code in the victim's browser, potentially stealing session cookies, redirecting users to malicious sites, or performing unauthorized actions on behalf of authenticated users. The vulnerability's impact extends beyond simple data theft as it can enable attackers to establish persistent access to the compromised system through session hijacking or by leveraging the authenticated context to perform administrative actions.
From an operational standpoint, QNAP devices running affected versions of QcalAgent present significant risks to organizations relying on these network-attached storage solutions. The vulnerability affects the device's web management interface, making it accessible to remote attackers without requiring physical access or prior authentication. This characteristic aligns with ATT&CK technique T1071.004 which covers application layer protocol: web protocols, and demonstrates how attackers can leverage web-based attack vectors to compromise network infrastructure. The attack surface is particularly concerning given that QNAP devices are commonly deployed in enterprise environments where they serve as critical storage solutions, making successful exploitation potentially devastating for data integrity and availability.
Organizations must prioritize immediate remediation of this vulnerability by upgrading to QcalAgent version 1.1.7 or later as recommended by the vendor. The mitigation strategy should include comprehensive network monitoring to detect potential exploitation attempts and implementation of web application firewalls to filter malicious traffic. Additional security measures should encompass regular vulnerability assessments of network infrastructure, network segmentation to limit access to affected devices, and user education regarding suspicious web content. The remediation process should also include verification of the upgrade through configuration audits and security scanning to ensure that all affected components have been properly updated. Security teams should implement continuous monitoring procedures to detect any potential exploitation attempts and maintain updated threat intelligence feeds to identify emerging attack patterns targeting similar vulnerabilities in network infrastructure devices.