CVE-2021-39150 is a high-severity vulnerability in XStream, a library used for serializing objects to XML. This vulnerability allows remote attackers to exploit affected versions of XStream by manipulating the processed input stream, potentially gaining access to internal resources that are not publicly available. It is critical for organizations to understand the implications of this vulnerability, as it can lead to unauthorized data access.
With a CVSS score of 8.5, this vulnerability is classified as high severity. The attack vector is network-based, and the complexity is rated as high, meaning exploitation requires specific conditions to be met. However, organizations that have implemented XStream's security framework correctly with a whitelist of required types are not affected. Those relying on the default blacklist should upgrade to at least version 1.4.18 to ensure security.
The urgency for defenders cannot be overstated; organizations should prioritize patching immediately to protect against potential exploits. The risk to organizations includes unauthorized access to sensitive internal data, which could have severe implications for data privacy and security.
As of now, there is confirmed knowledge of exploitation in the wild, further increasing the urgency for organizations to address this vulnerability. Security teams must act swiftly to mitigate risks associated with CVE-2021-39150.
Vulnerability Details
The official CVE description states that this vulnerability allows a remote attacker to request data from internal resources that are not publicly available by manipulating the processed input stream with specific Java runtime versions. The vulnerability is linked to CWE-502 (Deserialization of Untrusted Data) and CWE-918 (Server-Side Request Forgery).
The CVSS score of 8.5 indicates a high severity level due to the potential for significant confidentiality, integrity, and availability impacts. Affected versions include XStream and various distributions of Linux, such as Fedora and Debian.
Technical Analysis
The root cause of CVE-2021-39150 lies in the improper handling of input streams within the XStream library. The attack vector is network-based, meaning an attacker can exploit this vulnerability remotely. The complexity of the attack is considered high, as it requires knowledge of the system's configuration and the ability to manipulate the input stream effectively.
Exploitation requires low privileges, and no user interaction is necessary, which heightens the vulnerability's risk profile. The impact on confidentiality, integrity, and availability is rated as high, as attackers could potentially access and manipulate sensitive internal resources.
Risk & Impact Analysis
Organizations using affected versions of XStream face a significant risk of unauthorized data access, which can lead to data breaches and compliance violations. The blast radius for this vulnerability is broad, impacting various applications and services relying on XStream for XML serialization.
Given the high CVSS score and the confirmed exploitation, organizations must assess their exposure and prioritize remediation. The urgency for patching is critical, with a clear recommendation to update to version 1.4.18 or later to mitigate the risk effectively.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | Yes |
Public PoC | Yes |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The following versions of XStream and associated products are affected: all versions prior to 1.4.18, Fedora versions 33, 34, and 35, Debian versions 9.0, 10.0, and 11.0, and several Oracle products. Organizations should ensure they are running patched versions.
Mitigation & Remediation
Organizations should prioritize upgrading to XStream version 1.4.18 or later to mitigate this vulnerability. If immediate updates are not feasible, consider implementing strict input validation and using a custom security framework with a whitelist of allowed types.
For additional security measures, organizations can benefit from penetration testing to identify vulnerabilities and assess the effectiveness of their security controls.
Detection Guidance
Monitoring for unusual access patterns, especially attempts to access internal resources from external sources, can help in detecting potential exploitation of this vulnerability. Organizations should review logs for any unauthorized requests or suspicious input patterns.
AppSecure Threat Intelligence Insight
CVE-2021-39150 highlights the importance of robust input validation and configuration management. Organizations should ensure proper security frameworks are in place and avoid relying solely on default settings.
This vulnerability serves as a reminder of the potential risks associated with deserialization flaws. Security teams must stay vigilant and regularly assess their systems for vulnerabilities, employing best practices in application security.
For further reading on vulnerability management strategies, consider reviewing our guide on vulnerability management programs and explore the benefits of penetration testing methodologies for identifying security gaps.
Known Exploitation Timeline
As of now, CVE-2021-39150 is not included in the Known Exploited Vulnerabilities (KEV) catalog, indicating that there are no confirmed cases of active exploitation in the wild at this time.
EPSS Risk Context
The EPSS score for CVE-2021-39150 is 0.024, placing it in the 85th percentile, indicating a relatively high probability of exploitation.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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