CVE-2021-21351 is a medium severity vulnerability found in Apache XStream, a Java library used for serializing objects to XML. This vulnerability allows remote attackers to load and execute arbitrary code from a remote host by manipulating the processed input stream. The vulnerability affects all versions of XStream prior to 1.4.16, and if organizations have implemented the recommended security framework with a whitelist of minimal required types, they should not be affected.
The vulnerability has a CVSS score of 5.4, indicating medium severity. It is critical for organizations utilizing XStream to understand that failure to upgrade to version 1.4.16 or later may expose them to substantial risks, including unauthorized remote code execution. Given the impact of this vulnerability, organizations should prioritize patching immediately.
The potential risk to organizations includes exploitation by remote attackers, who may leverage this vulnerability to execute arbitrary code that could compromise system integrity and confidentiality. Additionally, the requirement for user interaction adds complexity to exploitation but does not eliminate the risk, particularly for applications not using a secure configuration.
As of now, there are no known public exploits for this vulnerability. However, organizations should remain vigilant and be prepared for potential exploitation attempts, given the nature of the vulnerability and the widespread use of XStream in various applications.
Organizations using affected versions of XStream should address this vulnerability in their priority patch cycle, as the risks associated with its exploitation can lead to significant security incidents.
Vulnerability Details
XStream is a Java library that facilitates the serialization of objects to XML. The vulnerability present in versions before 1.4.16 could allow remote code execution through manipulated input streams. The official CVE description highlights that if organizations follow the recommended configuration using a whitelist, they may not be affected.
The vulnerability is classified under multiple CWEs, including CWE-434 (Unrestricted Upload of File with Dangerous Type) and CWE-502 (Deserialization of Untrusted Data), indicating the potential for serious security risk if exploited.
The CVSS score of 5.4 indicates a medium severity level, with the attack vector being network-based. Attack complexity is considered high, requiring elevated privileges and user interaction, which complicates exploitation but does not diminish the associated risks.
Technical Analysis
The root cause of CVE-2021-21351 stems from the handling of input streams in XStream versions prior to 1.4.16, where improper validation allows for the execution of arbitrary code. The attack vector is network-based, and the exploitation process requires local access and high privileges, making it less likely for average users to encounter the exploit.
Given that user interaction is required, the vulnerability is more likely to be exploited in environments where user interactions with untrusted input can occur. The confidentiality impact is minimal, but the integrity impact is high, as successful exploitation can compromise application data.
Risk & Impact Analysis
The real-world deployment risk of this vulnerability is significant, especially for organizations that rely on XStream for XML serialization in critical applications. The potential for arbitrary code execution can lead to data breaches and integrity loss, which could have a cascading effect on business operations.
Organizations should consider the blast radius of such an exploit, which can affect not only the application utilizing XStream but also other systems connected to it. Given the CVSS score and the current threat landscape, organizations should address this vulnerability in their patch management processes.
With a 99.7 percentile EPSS score of 0.92, the urgency to remediate this vulnerability is underscored. Organizations should prioritize patching immediately to mitigate potential exploitation.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The affected versions of XStream are all versions prior to 1.4.16. This vulnerability also impacts various components including Apache ActiveMQ and JMeter, among others listed in the configurations.
Mitigation & Remediation
Organizations should upgrade to XStream version 1.4.16 or later to mitigate this vulnerability. If an immediate upgrade is not feasible, implementing a strict whitelist in the security framework can help protect against exploitation.
It is advisable to conduct regular security assessments and consider leveraging our application security assessments to identify potential vulnerabilities in the system.
Detection Guidance
Monitor for unusual input streams being processed by the application, as this could indicate an attempt to exploit the vulnerability. Additionally, logging and alerting on any unauthorized access attempts can help organizations detect potential exploitation.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2021-21351 highlights the ongoing risks associated with deserialization vulnerabilities. Organizations must ensure that they are not only remediating known vulnerabilities but also adopting a proactive security posture.
Security teams should use this vulnerability as a learning opportunity to enhance their security frameworks, ensuring that proper validation and whitelisting are in place. For more information on improving your security posture, consider our vulnerability management program and review our penetration testing methodology to stay ahead of potential threats.
For specific strategies on securing your applications, explore our insights on web application penetration testing which can help identify vulnerabilities like CVE-2021-21351.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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