CVE-2019-15614 in Nextcloud App
Summary
by MITRE
Missing sanitization in the iOS App 2.24.4 causes an XSS when opening malicious HTML files.
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Analysis
by VulDB Data Team • 02/05/2020
The vulnerability identified as CVE-2019-15614 represents a critical cross-site scripting flaw within the iOS App version 2.24.4 that arises from inadequate input sanitization mechanisms. This security weakness specifically manifests when the application processes and renders malicious HTML files, creating an avenue for attackers to execute arbitrary code within the context of the user's session. The vulnerability stems from the application's failure to properly validate and sanitize user-supplied HTML content before rendering it in the browser environment, allowing malicious payloads to be injected and executed without proper security controls. Such a flaw fundamentally compromises the application's security posture and exposes users to potential exploitation through seemingly benign file attachments or web content.
The technical implementation of this vulnerability aligns with CWE-79, which specifically addresses cross-site scripting vulnerabilities arising from insufficient input validation and sanitization. The flaw operates by bypassing the application's security filters that should normally prevent malicious scripts from executing within the application's rendering context. When a user opens a specially crafted HTML file, the application's inadequate sanitization routines fail to strip or encode potentially dangerous script elements, allowing attackers to inject malicious JavaScript code that executes in the user's browser session. This particular vulnerability demonstrates a classic failure in the principle of least privilege and input validation, where the application assumes that user-provided content is safe without proper security checks.
The operational impact of CVE-2019-15614 extends beyond simple script execution, as it enables attackers to perform a wide range of malicious activities including session hijacking, data theft, and privilege escalation within the application's context. An attacker could potentially leverage this vulnerability to steal user credentials, access sensitive information, or redirect users to malicious websites that appear legitimate. The vulnerability is particularly dangerous because it requires no special privileges or complex attack vectors, making it accessible to threat actors with minimal technical expertise. The attack surface is broadened by the fact that the vulnerability can be triggered through various file types that contain HTML content, including documents, emails, or web pages that users might encounter in normal browsing or file handling activities.
Mitigation strategies for this vulnerability should focus on implementing robust input sanitization and validation mechanisms within the application's HTML processing pipeline. Organizations should ensure that all user-supplied content undergoes strict sanitization before rendering, utilizing established libraries and frameworks designed specifically for HTML content sanitization. The implementation of content security policies and proper encoding of user input can significantly reduce the risk of exploitation. Additionally, regular security updates and patches should be deployed immediately upon vendor release to address the vulnerability, as the flaw exists in a specific application version and can be resolved through software updates. Security awareness training for users about the risks of opening untrusted HTML files and maintaining updated software versions represents a crucial defensive measure against this type of attack vector. The vulnerability also highlights the importance of following secure coding practices and conducting regular security assessments to identify and remediate similar issues in application code.