The vulnerability identified as CVE-2021-21353 is a medium-severity issue affecting the pug template engine, a popular npm package. This vulnerability allows for remote code execution if a remote attacker can control the `pretty` option of the pug compiler. Specifically, if user-provided objects, such as query parameters, are spread into the pug template inputs, attackers can exploit this to execute arbitrary code on the node.js backend. This issue has been addressed in version 3.0.1 of pug, and a backported fix is also available in version 2.0.3 of pug-code-gen.
The advisory applies to multiple pug packages, including "pug" and "pug-code-gen". It is important to note that this vulnerability is not exploitable if there is no way to pass untrusted input to pug as the `pretty` option. For instance, if templates are precompiled before user input is applied, upgrading to the latest version is not necessary.
Given the potential for significant impact, organizations using affected versions of pug should prioritize upgrading to mitigate the risk associated with this vulnerability. With a CVSS score of 6.8, the urgency for remediation is categorized as medium, indicating that organizations should address this vulnerability in their patch cycle.
As of now, the vulnerability has been publicly disclosed, and while a proof of concept (PoC) is available on GitHub, no known exploits have been confirmed in the wild. However, organizations should remain vigilant and consider implementing additional security measures to protect their applications.
Organizations should prioritize patching immediately.
Vulnerability Details
The official CVE description states that the vulnerability in pug allows for remote code execution when the `pretty` option is manipulated. The CVSS score from the NVD assigns a critical severity with a score of 9.0, which indicates a high risk due to the potential for significant impact on confidentiality, integrity, and availability.
This vulnerability affects the following products: pug and pug-code-gen. The publication date of this vulnerability is March 3, 2021. The associated CWE classifications include CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component) and CWE-94 (Improper Control of Generation of Code).
Technical Analysis
The root cause of this vulnerability lies in the improper handling of the `pretty` option within the pug template engine. Attackers may exploit this vulnerability by sending crafted requests, allowing them to control the behavior of the pug compiler. The attack vector for this vulnerability is network-based, with high attack complexity. Importantly, no privileges are required to exploit this vulnerability, and user interaction is not needed.
Regarding the impacts: the confidentiality impact is none, the integrity impact is high, and the availability impact is none. This means while the attack does not disrupt services, it can lead to unauthorized code execution, which can compromise data integrity.
Risk & Impact Analysis
The deployment of this vulnerability poses significant risks to organizations, particularly those utilizing the pug template engine in web applications. Attackers may leverage this vulnerability to execute arbitrary code, which could lead to unauthorized access or data manipulation. The blast radius of this vulnerability could extend to any application using the affected versions of pug, potentially impacting sensitive user data.
Given the CVSS score of 6.8 and the current absence from the KEV catalog, organizations should still treat this vulnerability with a high degree of urgency. The presence of a public PoC indicates that the vulnerability could be exploited if left unpatched, necessitating immediate attention in the patch cycle.
Signal | Status |
|---|---|
Known Exploit | Yes |
Public PoC | Yes |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The vulnerability affects multiple versions of pug, specifically all versions prior to 3.0.1 and pug-code-gen versions prior to 2.0.3. Organizations should review their dependencies and update to the latest versions to mitigate risks.
Mitigation & Remediation
To remediate this vulnerability, organizations should upgrade to pug version 3.0.1 or later. For those using pug-code-gen, it's essential to update to version 2.0.3 or later. If immediate patching is not possible, consider implementing workarounds such as compiling templates in advance to prevent untrusted input from being processed.
For more comprehensive security assessments, organizations may consider engaging in application security assessments to identify potential vulnerabilities or weaknesses.
Detection Guidance
Organizations should monitor logs for unusual activity related to template processing, as well as any attempts to manipulate the `pretty` option within pug. Behavioral anomalies and unexpected code execution should be investigated promptly to mitigate any potential damage.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2021-21353 highlights the critical need for secure coding practices in template engines and the potential impact of arbitrary code execution vulnerabilities. Security teams should focus on rigorous input validation and adherence to security best practices to prevent similar vulnerabilities.
This vulnerability underscores a larger trend in web application security, where template engines become targets for exploitation. Organizations need to remain vigilant and proactive in their security posture. For further guidance on securing applications, organizations can refer to the penetration testing methodology and the importance of regular security assessments.
Additionally, organizations can benefit from understanding the implications of vulnerability management, which can be explored through the vulnerability management program design to enhance their overall security strategy.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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