Description
Templates do not properly consider backticks (`) as Javascript string delimiters, and do not escape them as expected. Backticks are used, since ES6, for JS template literals. If a template contains a Go template action within a Javascript template literal, the contents of the action can be used to terminate the literal, injecting arbitrary Javascript code into the Go template. As ES6 template literals are rather complex, and themselves can do string interpolation, the decision was made to simply disallow Go template actions from being used inside of them (e.g., "var a = {{.}}"), since there is no obviously safe way to allow this behavior. This takes the same approach as github.com/google/safehtml. With fix, Template. Parse returns an Error when it encounters templates like this, with an ErrorCode of value 12. This ErrorCode is currently unexported but will be exported in the release of Go 1.21. Users who rely on the previous behavior can re-enable it using the GODEBUG flag jstmpllitinterp=1, with the caveat that backticks will now be escaped. This should be used with caution.
EPSS Score:
1%
Comprehensive Technical Analysis of EUVD-2023-33022
1. Vulnerability Assessment and Severity Evaluation
Vulnerability Description: The vulnerability EUVD-2023-33022 pertains to the improper handling of backticks (`) as JavaScript string delimiters in templates. Specifically, Go template actions within JavaScript template literals can be exploited to inject arbitrary JavaScript code. This issue arises because ES6 template literals are complex and can perform string interpolation, making it difficult to safely allow Go template actions within them.
Severity Evaluation:
The vulnerability has a CVSS Base Score of 9.8, indicating a critical severity level. The CVSS vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H signifies:
- Attack Vector (AV): Network (N)
- Attack Complexity (AC): Low (L)
- Privileges Required (PR): None (N)
- User Interaction (UI): None (N)
- Scope (S): Unchanged (U)
- Confidentiality (C): High (H)
- Integrity (I): High (H)
- Availability (A): High (H)
This high severity score underscores the potential for significant impact on confidentiality, integrity, and availability.
2. Potential Attack Vectors and Exploitation Methods
Attack Vectors:
- Remote Code Execution (RCE): An attacker could exploit this vulnerability to inject malicious JavaScript code into the Go template, leading to RCE.
- Cross-Site Scripting (XSS): If the template is used in a web application, an attacker could inject JavaScript code to perform XSS attacks, potentially stealing user data or manipulating the application.
Exploitation Methods:
- Template Injection: By crafting a template that includes a Go template action within a JavaScript template literal, an attacker can terminate the literal and inject arbitrary JavaScript code.
- String Interpolation: The complexity of ES6 template literals, which support string interpolation, can be leveraged to inject malicious code.
3. Affected Systems and Software Versions
Affected Software:
- Zabbix:
- Versions 6.4.0 to 6.4.2
- Versions 5.0.0 to 5.0.34
- Versions 6.0.0 to 6.0.17
Vendor:
- Zabbix
4. Recommended Mitigation Strategies
Immediate Mitigation:
- Update Software: Upgrade to the latest patched versions of Zabbix.
- Disable Unsafe Behavior: Use the
GODEBUGflagjstmpllitinterp=1with caution to re-enable the previous behavior, ensuring backticks are escaped.
Long-Term Mitigation:
- Code Review: Conduct thorough code reviews to ensure templates are securely handled.
- Input Validation: Implement robust input validation and sanitization to prevent injection attacks.
- Security Training: Educate developers on secure coding practices, especially regarding template handling and JavaScript string delimiters.
5. Impact on European Cybersecurity Landscape
Impact Analysis:
- Widespread Use: Zabbix is widely used for monitoring and managing IT infrastructure, making this vulnerability a significant risk for organizations relying on it.
- Critical Infrastructure: The potential for RCE and XSS attacks could compromise critical infrastructure, leading to data breaches, service disruptions, and financial losses.
- Compliance: Organizations must ensure compliance with regulations such as GDPR, which mandates robust security measures to protect personal data.
6. Technical Details for Security Professionals
Technical Overview:
- Template Parsing: The vulnerability occurs during the parsing of templates where Go template actions are used within JavaScript template literals.
- Error Handling: The fix involves
Template.Parsereturning an error with anErrorCodeof value 12 when encountering unsafe templates. ThisErrorCodewill be exported in Go 1.21. - Backtick Escaping: Users relying on the previous behavior can use the
GODEBUGflagjstmpllitinterp=1to re-enable it, ensuring backticks are escaped.
Recommendations:
- Monitoring: Implement continuous monitoring to detect and respond to any suspicious activities related to template parsing.
- Patch Management: Ensure a robust patch management process to apply updates promptly.
- Security Audits: Regularly conduct security audits and penetration testing to identify and mitigate similar vulnerabilities.
Conclusion: EUVD-2023-33022 is a critical vulnerability that requires immediate attention from organizations using affected versions of Zabbix. By understanding the technical details and implementing the recommended mitigation strategies, security professionals can effectively protect their systems and data from potential exploitation.