CVE-2026-105080 in ConvertX
Summary
by MITRE • 10/03/2026
In ConvertX before 0.19.0, converters/calibre.ts does not block recipe files, and instead passes them to the ebook-convert program from Calibre. This affects executable code in a .recipe or .downloaded_recipe file.
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Analysis
by VulDB Data Team • 10/03/2026
The vulnerability identified in ConvertX prior to version 0.19.0 represents a critical server-side request forgery and arbitrary code execution flaw rooted in improper input validation within the application's conversion logic. Specifically, the module responsible for handling Calibre-based conversions fails to restrict file types passed to the underlying ebook-convert utility. This oversight allows an attacker to supply maliciously crafted recipe files with extensions such as .recipe or .downloaded_recipe instead of standard document formats like PDF, EPUB, or MOBI. The core technical failure lies in the absence of strict allow-listing for input filenames and content types, which results in the application blindly trusting user-supplied file metadata without verifying that the payload aligns with expected safe behaviors.
From a technical perspective, Calibre's ebook-convert tool is designed to process various e-book formats, but it also supports recipe files which are essentially Python scripts used to download and format content from websites for offline reading. These recipes have full access to system resources and can execute arbitrary commands on the host machine where they run. By allowing a user-uploaded .recipe file to be processed directly by ebook-convert without sanitization or sandboxing, ConvertX effectively creates an execution vector that bypasses standard security controls. When the application invokes the conversion process with this malicious input, it triggers the Python interpreter embedded within Calibre's environment, leading to the immediate execution of any code contained within the recipe file. This mechanism transforms a simple document upload feature into a remote code execution pathway, assuming the service runs with sufficient privileges to execute system commands or access sensitive data.
The operational impact of this vulnerability is severe, particularly in environments where ConvertX processes documents from untrusted sources such as public web portals or user-generated content platforms. An authenticated attacker could exploit this flaw to achieve complete compromise of the server hosting the application. This includes reading sensitive configuration files, exfiltrating database credentials stored on disk, installing persistent backdoors, or pivoting to other systems within the internal network depending on the isolation level of the container or host environment. In cloud-native deployments, this could lead to lateral movement if instance metadata services are accessible from the compromised application context. The lack of input validation means that even users with low-level privileges can escalate their access significantly by leveraging the elevated permissions typically required for document conversion processes.
This vulnerability aligns closely with CWE-94 Improper Control of Generation of Code, specifically code injection via untrusted inputs, and falls under the broader category of CWE-20 Improvement in Input Validation. In terms of adversary tactics, this exploitation technique maps to MITRE ATT&CK T1505 Server Software Component, where attackers install or execute malicious components within legitimate software services to maintain persistence or achieve initial access. It also relates to T1059 Command and Scripting Interpreter, as the attack leverages Python scripts executed by a trusted application binary. The failure to implement strict file type restrictions is a classic example of CWE-434 Unrestricted Upload of File with Dangerous Type, which remains one of the most prevalent causes of web application compromises in document processing systems.
To mitigate this risk, immediate remediation involves upgrading ConvertX to version 0.19.0 or later, where the developers have implemented proper filtering mechanisms for recipe files. In addition to updating the software, organizations should enforce strict allow-listing of accepted file extensions at both the application layer and any preceding reverse proxy or web server configuration. Implementing content-type verification that checks not just the extension but also the magic numbers within the uploaded file can provide an additional layer of defense against spoofed filenames. Furthermore, running document conversion services in isolated containers with minimal privileges and restricted network access will limit the blast radius if a vulnerability is exploited. Enabling sandboxing for any external tools invoked by the application ensures that even successful exploitation does not lead to full system compromise. Regular security audits focusing on input validation patterns across all file processing endpoints are essential to prevent similar vulnerabilities from being introduced in future updates or custom integrations.