CVE-2021-42560 in CALDERA
Summary
by MITRE • 01/12/2022
An issue was discovered in CALDERA 2.9.0. The Debrief plugin receives base64 encoded "SVG" parameters when generating a PDF document. These SVG documents are parsed in an unsafe manner and can be leveraged for XXE attacks (e.g., File Exfiltration, Server Side Request Forgery, Out of Band Exfiltration, etc.).
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Analysis
by VulDB Data Team • 01/15/2022
The vulnerability identified as CVE-2021-42560 affects CALDERA version 2.9.0 and resides within the Debrief plugin functionality. This issue represents a critical security flaw that arises from improper handling of base64 encoded SVG parameters during PDF document generation processes. The vulnerability stems from the unsafe parsing of SVG content which allows malicious actors to inject malicious XML entities that can be exploited for various attack vectors. The Debrief plugin's implementation fails to properly sanitize or validate the incoming SVG data before processing it, creating an avenue for exploitation that directly impacts the security posture of systems utilizing this version of the CALDERA framework.
The technical implementation of this vulnerability manifests through the XML External Entity processing mechanism within the SVG parsing functionality. When the Debrief plugin receives base64 encoded SVG parameters, it decodes and processes these documents without adequate security controls to prevent malicious entity references. This unsafe parsing behavior enables attackers to construct specially crafted SVG files containing XML external entity declarations that can trigger server-side request forgery, file exfiltration, or out-of-band data exfiltration attacks. The vulnerability specifically aligns with CWE-611 (Improper Restriction of XML External Entity Reference) and represents a classic example of how XML processing libraries can be exploited when proper input validation and entity resolution controls are not implemented. The attack surface extends beyond simple file access to include potential network-based attacks that can bypass traditional firewall restrictions.
The operational impact of CVE-2021-42560 is significant for organizations utilizing CALDERA 2.9.0, particularly those in threat intelligence and red team operations where the framework's Debrief plugin is actively used. Attackers can leverage this vulnerability to extract sensitive information from the server hosting the CALDERA instance, potentially accessing internal system files, credentials, or other confidential data. The server-side request forgery component allows adversaries to use the compromised CALDERA server as an intermediary to probe internal networks or exfiltrate data through out-of-band channels. This vulnerability particularly affects environments where CALDERA is deployed in production or operational security contexts where the framework's PDF generation capabilities are utilized. The impact extends to potential compromise of the entire operational environment as attackers can use this vector to escalate privileges or gain unauthorized access to additional system resources.
Mitigation strategies for CVE-2021-42560 should prioritize immediate remediation through the deployment of CALDERA version 3.0.0 or later, which contains the necessary patches to address the unsafe XML parsing behavior. Organizations should implement strict input validation and sanitization controls for all SVG content processed by the Debrief plugin, ensuring that any external entity references are properly restricted or disabled. Network-level mitigations should include implementing web application firewalls with content filtering capabilities to detect and block suspicious SVG content patterns. Security teams should also consider disabling the Debrief plugin functionality entirely if it is not actively required, or implementing additional access controls to limit who can invoke the PDF generation capabilities. The implementation of proper XML parsing libraries with disabled external entity resolution, as recommended in the OWASP XML External Entity Prevention Cheat Sheet, should be enforced across all affected systems. Organizations should conduct comprehensive security assessments to identify any potential exploitation attempts and implement monitoring controls to detect anomalous SVG processing activities that may indicate attempted exploitation of this vulnerability.