CVE-2021-3395 in Pryaniki
Summary
by MITRE • 02/03/2021
A cross-site scripting (XSS) vulnerability in Pryaniki 6.44.3 allows remote authenticated users to upload an arbitrary file. The JavaScript code will execute when someone visits the attachment.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 02/22/2021
The vulnerability identified as CVE-2021-3395 represents a critical cross-site scripting flaw in the Pryaniki application version 6.44.3 that enables authenticated attackers to execute malicious JavaScript code through file upload functionality. This vulnerability resides within the application's file handling mechanisms and specifically targets the way the system processes and displays uploaded attachments. The flaw allows an attacker with valid credentials to upload a specially crafted file that contains malicious javascript code, which then executes in the context of other users who view the attachment.
The technical exploitation of this vulnerability follows a classic XSS attack pattern where the application fails to properly sanitize or validate user-supplied input during the file upload process. When an authenticated user uploads a file containing malicious javascript, the system stores this file without adequate sanitization measures. Subsequently, when other users navigate to the page displaying the attachment, their browsers execute the embedded javascript code within the context of their authenticated session. This creates a persistent XSS vector that can be leveraged to steal session cookies, perform unauthorized actions on behalf of victims, or redirect users to malicious websites.
From an operational impact perspective, this vulnerability presents a significant risk to organizations using Pryaniki 6.44.3 as it allows attackers to compromise user sessions and potentially escalate privileges within the application. The authenticated nature of the attack means that attackers do not need to perform initial exploitation through external means but can leverage existing user credentials to gain access to the application's functionality. The persistence of the vulnerability means that once a malicious file is uploaded, it continues to affect users until the file is removed from the system or the vulnerability is patched.
The vulnerability aligns with CWE-79 which describes Cross-Site Scripting flaws in web applications, specifically addressing the improper neutralization of input during web page generation. This weakness allows attackers to inject malicious scripts that execute in the victim's browser context. The attack pattern follows the MITRE ATT&CK framework's technique T1566 which covers social engineering attacks including spearphishing with a link, where the malicious file serves as the payload that executes upon user interaction. Organizations should implement strict input validation and output encoding measures to prevent such vulnerabilities, including sanitizing uploaded files, implementing proper content security policies, and ensuring that file uploads do not execute code within the application's web context.
The mitigation strategy for CVE-2021-3395 requires immediate patching of the Pryaniki application to version 6.44.4 or later, which contains the necessary security fixes. Organizations should also implement additional defensive measures such as strict file type validation, content scanning for uploaded files, and the implementation of web application firewalls that can detect and block malicious script execution attempts. Regular security testing including dynamic application security testing and static code analysis should be conducted to identify similar vulnerabilities in other applications. Additionally, user education regarding suspicious file attachments and implementing principle of least privilege access controls can help minimize the potential impact of successful exploitation attempts.