CVE-2019-20802 in Documents App
Summary
by MITRE
An issue was discovered in the Readdle Documents app before 6.9.7 for iOS. The application's file-transfer web server improperly displays directory names, leading to Stored XSS, which may be used to steal a user's data. This requires user interaction because there is no known direct way for an attacker to create a crafted directory name on a victim's device. However, a crafted directory name can occur if a victim extracts a ZIP archive that was provided by an attacker.
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Analysis
by VulDB Data Team • 05/18/2020
The vulnerability identified as CVE-2019-20802 affects the Readdle Documents iOS application, specifically versions prior to 6.9.7, presenting a significant security risk through a stored cross-site scripting flaw. This issue arises from the application's web server implementation that handles file transfers, where directory names are improperly displayed within the web interface without adequate sanitization or encoding mechanisms. The flaw exists in the application's handling of directory listings, creating a pathway for malicious code execution when users interact with compromised file structures.
The technical nature of this vulnerability stems from the application's failure to properly escape or sanitize directory names before rendering them in the web interface context. When a user extracts a maliciously crafted ZIP archive containing specially formatted directory names, these names are displayed in the application's web server interface without proper HTML encoding. This creates an environment where malicious JavaScript code embedded within directory names can be executed in the context of the user's browser session, potentially allowing attackers to steal session cookies, credentials, or other sensitive data. The vulnerability is categorized as a stored XSS issue under CWE-79, which specifically addresses the improper handling of untrusted data within web applications.
The operational impact of this vulnerability requires specific user interaction to exploit, as attackers cannot directly create malicious directory names on victim devices. However, the attack vector becomes viable when victims unknowingly extract ZIP archives provided by attackers, making this a social engineering-driven exploit. The attack chain begins with an attacker distributing a malicious archive, continues through user extraction of the archive, and concludes with the execution of stored XSS payloads when the application displays the compromised directory names. This dependency on user interaction makes the vulnerability less immediately dangerous but still highly concerning due to its potential for data exfiltration and session hijacking.
The security implications extend beyond simple data theft, as this vulnerability could enable attackers to perform actions on behalf of users within the application context, potentially leading to unauthorized file access, modification, or deletion. The web server component of the application becomes a potential attack surface where malicious code execution can occur, particularly when users interact with file listings or directory structures. This vulnerability aligns with ATT&CK techniques related to credential access and execution through malicious file content, where the attack leverages legitimate application functionality to deliver malicious payloads.
Mitigation strategies for this vulnerability include updating to Readdle Documents version 6.9.7 or later, which implements proper input sanitization and output encoding for directory names. Users should exercise caution when extracting archives from untrusted sources and should verify the integrity of downloaded files before processing. Security awareness training for end users regarding the dangers of extracting unknown archives and the importance of keeping applications updated should be emphasized. Network administrators should monitor for suspicious file transfer activities and consider implementing content filtering solutions that can detect and block potentially malicious archive content. Additionally, organizations should ensure that mobile device management policies include regular application updates and security assessments to prevent exploitation of such vulnerabilities.