CVE-2020-9359 in okular
Summary
by MITRE
KDE Okular before 1.10.0 allows code execution via an action link in a PDF document.
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Analysis
by VulDB Data Team • 05/11/2025
The vulnerability identified as CVE-2020-9359 represents a critical code execution flaw in KDE Okular, a popular PDF viewer application used across multiple operating systems including Linux, Windows, and macOS. This vulnerability specifically affects versions prior to 1.10.0 and stems from improper handling of action links embedded within PDF documents. The flaw enables attackers to craft malicious PDF files that, when opened in vulnerable versions of Okular, can execute arbitrary code on the victim's system with the privileges of the user running the application.
The technical implementation of this vulnerability resides in Okular's insufficient validation of action links contained within PDF files. When a PDF document contains an action link that triggers a specific sequence of operations, the application fails to properly sanitize or verify the link parameters before executing them. This improper input validation creates a path for attackers to inject malicious commands that can be interpreted and executed by the underlying operating system. The vulnerability is classified under CWE-74 as a "Improper Neutralization of Special Elements in Output Used by a Downstream Component" and can be categorized under ATT&CK technique T1059.007 for "Command and Scripting Interpreter: PowerShell" or similar execution methods depending on the target platform.
The operational impact of this vulnerability extends beyond simple code execution to encompass potential system compromise and data exfiltration. An attacker could craft a PDF document that, when opened by a victim using an affected version of Okular, automatically executes malicious payloads such as downloading additional malware, establishing reverse shells, or accessing sensitive system information. The attack vector is particularly concerning because PDF files are commonly shared through email attachments, file sharing platforms, and web downloads, making successful exploitation highly probable in real-world scenarios. The vulnerability affects users who frequently open PDF documents from untrusted sources, with no additional authentication or verification required for the malicious code to execute automatically upon document opening.
Mitigation strategies for CVE-2020-9359 primarily involve upgrading to KDE Okular version 1.10.0 or later, which includes proper input validation and sanitization of action links. System administrators should implement comprehensive patch management policies to ensure all vulnerable systems are updated promptly. Additionally, users should exercise caution when opening PDF documents from unknown or untrusted sources and consider using alternative PDF viewers for sensitive operations. Organizations may also implement network-based security controls such as PDF content filtering and sandboxing solutions to detect and prevent exploitation attempts. The vulnerability highlights the importance of proper input validation and secure coding practices in document processing applications, particularly those handling untrusted content from external sources.