CVE-2017-16043 in Shouts
Summary
by MITRE
Shout is an IRC client. Because the `/topic` command in messages is unescaped, attackers have the ability to inject HTML scripts that will run in the victim's browser. Affects shout >=0.44.0 <=0.49.3.
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Analysis
by VulDB Data Team • 03/21/2023
The vulnerability identified as CVE-2017-16043 represents a critical cross-site scripting flaw in the Shout IRC client software, which operates as a web-based chat interface for internet relay chat communications. This vulnerability specifically affects versions of Shout ranging from 0.44.0 through 0.49.3, creating a significant security risk for users who rely on this client for their communication needs. The flaw exists within the handling of the `/topic` command, which is a standard IRC command used to set or change the channel topic, making it a fundamental component of the client's functionality.
The technical nature of this vulnerability stems from insufficient input sanitization and output escaping mechanisms within the Shout client's processing of IRC messages. When users send messages containing the `/topic` command with maliciously crafted content, the application fails to properly escape special characters that could be interpreted as HTML or JavaScript code by web browsers. This lack of proper sanitization creates an environment where attackers can inject malicious scripts that execute automatically in the victim's browser context. The vulnerability directly maps to CWE-79, which describes cross-site scripting flaws where untrusted data is improperly handled and rendered in web contexts, and aligns with ATT&CK technique T1211 which covers the use of malicious HTML content to compromise user systems.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the ability to perform various malicious activities within the victim's browser session. Attackers could potentially steal session cookies, redirect users to malicious websites, inject additional harmful content, or even exploit other browser-based vulnerabilities that may be present. The attack vector is particularly concerning because it leverages legitimate IRC communication channels, making it difficult for users to distinguish between benign and malicious messages. Since Shout operates as a web-based client, any user who receives an IRC message containing the malicious topic command would be automatically vulnerable upon viewing the message, creating a widespread risk across all users of affected versions. This makes the vulnerability particularly dangerous in collaborative environments where multiple users share channels and receive messages from various sources.
Mitigation strategies for CVE-2017-16043 should prioritize immediate version updates to Shout 0.49.4 or later, which contains the necessary patches to properly escape HTML characters in topic commands. Organizations using Shout should also implement network-level monitoring to detect unusual IRC traffic patterns that might indicate exploitation attempts, and consider deploying web application firewalls to filter potentially malicious content. Additionally, users should be educated about the risks of clicking on untrusted IRC messages, particularly those containing topic changes, and administrators should regularly audit their Shout installations to ensure they are running patched versions. The vulnerability serves as a reminder of the critical importance of input validation and output escaping in web applications, particularly when handling user-generated content that may be displayed in browser contexts, and demonstrates how seemingly simple IRC commands can create substantial security risks when not properly secured against injection attacks.