CVE-2022-40276 in Zettlr
Summary
by MITRE • 11/04/2022
Zettlr version 2.3.0 allows an external attacker to remotely obtain arbitrary local files on any client that attempts to view a malicious markdown file through Zettlr. This is possible because the application does not have a CSP policy (or at least not strict enough) and/or does not properly validate the contents of markdown files before rendering them.
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Analysis
by VulDB Data Team • 05/03/2025
The vulnerability identified as CVE-2022-40276 represents a critical security flaw in Zettlr version 2.3.0 that enables remote code execution through arbitrary file access on client systems. This vulnerability stems from insufficient input validation and inadequate content security policies within the application's markdown rendering engine. The flaw allows external attackers to craft malicious markdown files that can trigger unauthorized file access when viewed by unsuspecting users, creating a significant attack surface that extends beyond typical web-based exploitation vectors.
The technical root cause of this vulnerability lies in the application's failure to implement proper content security policies and inadequate sanitization of markdown file contents during rendering. When Zettlr processes markdown files, it does not sufficiently validate the file structure or content before displaying it to users, particularly in how it handles file paths and references within the markdown syntax. This absence of proper validation creates opportunities for attackers to include malicious file references or embedded content that can trigger local file system access when the document is rendered. The vulnerability specifically affects the application's handling of relative paths and file inclusion mechanisms within markdown documents.
From an operational perspective, this vulnerability poses severe risks to users who may unknowingly open maliciously crafted markdown files, potentially leading to unauthorized access to sensitive local files, system information disclosure, and potential data exfiltration. The attack vector is particularly concerning because it can be delivered through email attachments, shared documents, or web-based markdown viewers, making it difficult for users to distinguish between legitimate and malicious content. The impact extends beyond simple file access to potentially enable further exploitation if the accessed files contain sensitive information or if the vulnerability can be chained with other exploits.
This vulnerability aligns with CWE-20, which describes improper input validation, and relates to ATT&CK technique T1059.001 for command and scripting interpreter. The lack of content security policy enforcement creates opportunities for attackers to manipulate the application's rendering behavior to access local resources. Organizations using Zettlr should implement immediate mitigations including updating to patched versions, implementing network-level restrictions on markdown file downloads, and educating users about the risks of opening untrusted markdown documents. Additional defensive measures should include network monitoring for suspicious file access patterns and implementing application whitelisting policies to restrict markdown file handling to trusted sources only.