CVE-2026-70383 in DigiDoc4
Summary
by MITRE • 08/20/2026
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') vulnerability in Estonian Information System Authority (RIA) DigiDoc4 client.
This issue affects DigiDoc4: from 4.0.0 before 4.11.0.
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Analysis
by VulDB Data Team • 08/20/2026
The Estonian Information System Authority, known as RIA, developed the DigiDoc4 software suite to facilitate secure digital signatures and encryption for documents within Estonia's e-residency and broader electronic governance infrastructure. A critical security flaw was identified in versions of this client ranging from 4.0.0 up to, but not including, version 4.11.0. This vulnerability is classified as an improper limitation of a pathname to a restricted directory, commonly referred to in the cybersecurity community as path traversal or directory traversal. The core technical flaw lies in how the application processes file paths provided by users or external inputs during operations such as saving signed documents, loading templates, or managing temporary files. Specifically, the software fails to adequately sanitize or validate input strings before using them to construct filesystem access requests. This lack of rigorous validation allows an attacker to manipulate path components, typically by inserting sequences like dot-dot-slash, which are interpreted by the operating system as instructions to navigate up the directory hierarchy from the intended target location.
From a technical perspective, this vulnerability exploits the fundamental behavior of file systems where relative paths can be used to escape sandboxed or restricted directories. When DigiDoc4 processes these maliciously crafted inputs without proper normalization or restriction checks, it may write sensitive data to arbitrary locations on the host system or read files from areas outside its designated scope. This capability effectively bypasses application-level security controls that rely on directory confinement to protect user privacy and system integrity. The impact of such a flaw is significant because DigiDoc4 operates with elevated privileges in many contexts, particularly when interacting with hardware tokens for digital signatures. An attacker who can trigger this vulnerability through a maliciously crafted document or link could potentially overwrite critical configuration files, inject malware into trusted directories, or exfiltrate sensitive personal and financial data stored on the user's machine.
The operational impact extends beyond simple file access violations. In the context of Estonia’s highly digitized society where DigiDoc4 is widely used for banking, government services, and legal transactions, a successful exploitation could undermine trust in the digital signature mechanism itself. If an attacker can manipulate files within directories that are monitored or signed by other applications, they might facilitate further attacks such as privilege escalation or persistence mechanisms. Furthermore, because the vulnerability affects versions starting from 4.0.0, it represents a long-standing issue present across multiple major releases of the software. This longevity highlights the importance of continuous security auditing and input validation practices in cryptographic client development. The flaw aligns with CWE-22, which defines improper limitation of pathname to restricted directory, and is associated with MITRE ATT&CK technique T1083, specifically file and directory discovery or manipulation, depending on whether the attacker seeks information or aims to alter system state.
Mitigation for this vulnerability requires immediate action by users and administrators relying on affected versions of DigiDoc4. The primary remediation strategy is to upgrade the software to version 4.11.0 or any subsequent release where RIA has implemented robust input validation mechanisms. These updates typically include strict whitelisting of allowed characters in file paths, normalization of path strings to resolve relative references before access, and explicit checks to ensure that resolved paths remain within expected directories. Additionally, users should exercise caution when opening documents from untrusted sources, as these could contain payloads designed to trigger the traversal logic during automatic processing or previewing functions. Security awareness training regarding the risks associated with digital signature applications can also help prevent accidental exploitation through social engineering vectors that might lead a user to interact with maliciously crafted files. Organizations should ensure their patch management processes are updated to prioritize this specific vulnerability given its potential for significant data compromise and system integrity violations.