CVE-2010-2480 in Mako
Summary
by MITRE
Mako before 0.3.4 relies on the cgi.escape function in the Python standard library for cross-site scripting (XSS) protection, which makes it easier for remote attackers to conduct XSS attacks via vectors involving single-quote characters and a JavaScript onLoad event handler for a BODY element.
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Analysis
by VulDB Data Team • 03/30/2025
The vulnerability identified as CVE-2010-2480 affects the Mako templating engine version 0.3.3 and earlier, representing a critical cross-site scripting weakness that undermines the security of web applications utilizing this framework. This vulnerability stems from the templating engine's reliance on the Python standard library's cgi.escape function for sanitizing user input and preventing XSS attacks. The flaw specifically manifests when handling single-quote characters within JavaScript onLoad event handlers for BODY elements, creating a pathway for malicious actors to bypass intended security measures and inject harmful scripts into web pages. The issue demonstrates a fundamental flaw in the security model of the templating engine, where the default sanitization mechanism fails to properly handle certain character sequences that could be exploited by attackers.
The technical implementation of this vulnerability exploits the limitations of the cgi.escape function, which does not adequately sanitize all potential XSS vectors, particularly when dealing with single-quote characters in specific contexts. When Mako processes templates containing user-supplied data, it relies on this function to escape special characters that could enable script execution. However, the function's behavior with single quotes in JavaScript contexts creates a gap that attackers can leverage. The vulnerability specifically targets scenarios where JavaScript code is embedded within BODY element onLoad handlers, where single-quote characters can be used to break out of string contexts and inject malicious payloads. This weakness allows attackers to craft payloads that bypass the intended escaping mechanism, enabling them to execute arbitrary JavaScript code in the context of victims' browsers.
The operational impact of this vulnerability extends beyond simple data theft or defacement, as it provides attackers with persistent access to user sessions and the ability to manipulate web application behavior. Remote attackers can exploit this vulnerability to inject malicious scripts that can steal cookies, redirect users to malicious sites, or perform actions on behalf of authenticated users. The vulnerability affects any web application using Mako templating engine versions prior to 0.3.4, making it particularly dangerous in environments where multiple applications rely on this framework. The ease of exploitation, combined with the potential for widespread impact, makes this vulnerability particularly concerning for organizations maintaining web applications that process user input through Mako templates.
Organizations should immediately upgrade to Mako version 0.3.4 or later to remediate this vulnerability, as this release includes proper XSS protection mechanisms that address the specific flaw in the cgi.escape function handling. Additionally, implementing proper input validation and output encoding at multiple layers of the application architecture provides defense-in-depth protection against similar vulnerabilities. Security teams should conduct comprehensive audits of their web applications to identify all instances where Mako templates are used and ensure proper sanitization practices are in place. The vulnerability aligns with CWE-79, which describes cross-site scripting flaws, and represents a specific instance of improper input handling that allows malicious code execution. From an ATT&CK perspective, this vulnerability maps to T1059.007 for JavaScript execution and T1566 for social engineering through malicious web content, highlighting the multi-faceted nature of the threat it represents.