CVE-2021-23980 is a medium-severity vulnerability affecting Mozilla's Bleach library. This vulnerability allows for a mutation cross-site scripting (XSS) attack when users call the bleach.clean method with specific parameters. The affected functionality includes support for SVG or Math elements within allowed tags such as <p> or <br>, but also includes other tags like <style>, <title>, <noscript>, <script>, <textarea>, <noframes>, <iframe>, or <xmp> if the keyword argument strip_comments is set to False. It's important to note that none of these tags are included in the default allowed tags, and the strip_comments parameter defaults to True, adding a layer of complexity to potential exploitation.
The vulnerability has a CVSS score of 6.1, indicating a medium severity level. This score reflects a network attack vector, low attack complexity, no privileges required, and the necessity of user interaction. The impact on confidentiality and integrity is classified as low, while availability is unaffected.
Risk to organizations includes potential exposure to XSS attacks, which can lead to unauthorized access to sensitive information or manipulation of web applications. Given the nature of the vulnerability, organizations utilizing the Bleach library should prioritize remediation efforts to mitigate the risks associated with this vulnerability.
Currently, there are no known exploits or public proof of concepts for CVE-2021-23980, and it has not been classified as actively exploited in the wild. However, organizations should be vigilant and apply patches as part of their security practices.
Vulnerability Details
The official description of CVE-2021-23980 states that it involves a mutation XSS vulnerability that affects users calling bleach.clean with specific tags and arguments. The vulnerability is associated with the following CWE classification: CWE-79.
The affected product is Mozilla Bleach, with the vulnerability impacting versions prior to 3.3.0. The vulnerability was published on February 16, 2023, and is currently marked as modified within the CVE database.
Technical Analysis
The root cause of this vulnerability lies in the handling of user inputs for the bleach.clean function, which does not adequately validate or sanitize inputs when certain tags are included. The attack vector is network-based, meaning an attacker can exploit this vulnerability remotely without physical access to the system.
The attack complexity is low, as it requires no special conditions for exploitation. However, user interaction is necessary, as the victim must trigger the vulnerable function with crafted input. This vulnerability has a low impact on confidentiality and integrity, as it may allow for the execution of arbitrary scripts, but does not affect system availability.
Risk & Impact Analysis
Organizations that deploy applications using the affected versions of Bleach are at risk of XSS attacks, potentially leading to unauthorized data access or manipulation. The blast radius for this vulnerability could be significant, depending on the application’s user base and the data handled. Thus, organizations should promptly address this vulnerability in their patch cycle to reduce the likelihood of exploitation.
Given the CVSS score of 6.1 and the current lack of known exploits, organizations should schedule remediation in their security management processes. Regular reviews of code that utilizes external libraries like Bleach can help identify and mitigate similar vulnerabilities proactively.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
All versions of Mozilla Bleach prior to version 3.3.0 are affected by this vulnerability. Organizations should ensure they are using the latest patched versions to mitigate the risks associated with CVE-2021-23980.
Mitigation & Remediation
To remediate this vulnerability, organizations should upgrade to the latest version of Mozilla Bleach, specifically version 3.3.0 or later. If immediate upgrades are not feasible, organizations should consider implementing workarounds such as restricting the use of the bleach.clean function with the aforementioned parameters and tags.
Additionally, organizations should conduct a thorough security assessment of their applications to identify potential vulnerabilities, and consider adopting regular security practices such as penetration testing to evaluate their security posture.
Detection Guidance
Organizations should monitor logs for unusual activity related to the bleach.clean function and review user interactions that may involve rendering untrusted inputs. Behavioral anomalies, such as unexpected script execution or unauthorized data access, should also be flagged for further investigation.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2021-23980 highlights the ongoing challenges in securing web applications, particularly those that allow for dynamic content rendering. This vulnerability serves as a reminder for security teams to regularly review input validation and sanitization practices to mitigate XSS risks.
Organizations should consider implementing robust security measures, including secure coding practices and regular security assessments. For further insights into enhancing application security, organizations can explore our vulnerability management program and invest in penetration testing methodology to proactively identify and address vulnerabilities.
Moreover, organizations should remain aware of evolving threat landscapes and adapt their security strategies accordingly by reviewing trends in vulnerability management and exploring modern security practices such as cloud penetration testing to enhance their overall security posture.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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