CVE-2011-5199 in tinyguestbook
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in sign.php in tinyguestbook allows remote attackers to inject arbitrary web script or HTML via the msg parameter.
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Analysis
by VulDB Data Team • 02/22/2019
The CVE-2011-5199 vulnerability represents a classic cross-site scripting flaw in the tinyguestbook application's sign.php script, which operates as a web-based guestbook system. This vulnerability specifically targets the msg parameter, which is used to capture user-submitted messages in the guestbook. The flaw exists in the application's input validation mechanisms, where user-provided data is not properly sanitized before being rendered back to other users. This creates an exploitable condition where malicious actors can inject arbitrary HTML or JavaScript code that executes in the context of other users' browsers when they view the guestbook entries. The vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is one of the most prevalent and well-documented web application security flaws. The ATT&CK framework categorizes this as a Web Application Attack, specifically under the technique of Code Injection where adversaries inject malicious code into web applications.
The technical implementation of this vulnerability stems from the application's failure to implement proper output encoding or input sanitization for user-supplied content. When a user submits a message through the sign.php form, the application processes the msg parameter without adequately escaping special HTML characters or validating the input against a whitelist of allowed characters. This allows attackers to embed script tags, event handlers, or other malicious code within the message content. The vulnerability is particularly dangerous because it affects the guestbook's display functionality, meaning any user who views the compromised entries becomes a victim of the XSS attack. The attack vector is straightforward - an attacker simply needs to submit a malicious payload through the message field, which then gets stored in the application's database and executed when other users browse the guestbook.
The operational impact of CVE-2011-5199 extends beyond simple script execution, as it can enable more sophisticated attacks. Attackers can leverage this vulnerability to steal session cookies, redirect users to malicious websites, deface the guestbook content, or perform actions on behalf of authenticated users. The vulnerability essentially transforms the guestbook into a vector for delivering malware or conducting phishing attacks against visitors. In a real-world scenario, this could allow attackers to hijack user sessions, capture sensitive information, or use the compromised application as a stepping stone for further attacks within the network. The vulnerability affects the integrity and confidentiality of the web application, potentially compromising user trust and the application's reputation.
Mitigation strategies for CVE-2011-5199 should focus on implementing robust input validation and output encoding practices. The most effective approach involves sanitizing all user inputs by implementing proper HTML entity encoding before rendering any user-provided content in the application's output. This can be achieved through the use of dedicated encoding functions or libraries that automatically escape special characters. Additionally, developers should implement a whitelist-based input validation system that only allows specific characters or patterns in the msg parameter. The application should also employ Content Security Policy headers to prevent the execution of unauthorized scripts, and implement proper session management to limit the damage that can be caused by stolen session tokens. Regular security code reviews and input validation testing should be conducted to prevent similar vulnerabilities from being introduced in future versions of the application. Organizations should also consider implementing web application firewalls and monitoring systems to detect and prevent exploitation attempts of such vulnerabilities.