CVE-2010-2477 in paste
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in the paste.httpexceptions implementation in Paste before 1.7.4 allow remote attackers to inject arbitrary web script or HTML via vectors involving a 404 status code, related to (1) paste.urlparser.StaticURLParser, (2) paste.urlparser.PkgResourcesParser, (3) paste.urlmap.URLMap, and (4) HTTPNotFound.
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Analysis
by VulDB Data Team • 09/28/2021
The CVE-2010-2477 vulnerability represents a significant cross-site scripting flaw within the Paste web framework's exception handling mechanism. This vulnerability affects versions of Paste prior to 1.7.4 and specifically targets the paste.httpexceptions implementation that manages HTTP error responses. The flaw occurs when the framework processes 404 status codes through various URL parsing components, creating opportunities for remote attackers to inject malicious scripts into web applications that utilize this framework. The vulnerability is particularly concerning because it operates at the framework level, potentially affecting numerous applications that depend on Paste for their web serving capabilities.
The technical exploitation of this vulnerability involves manipulating URL parsing components within the Paste framework to inject malicious content into 404 error responses. Specifically, the vulnerability manifests through four distinct parser classes: paste.urlparser.StaticURLParser, paste.urlparser.PkgResourcesParser, paste.urlmap.URLMap, and the HTTPNotFound handler itself. When these components process malformed URLs or request paths that result in 404 responses, they fail to properly sanitize user input before rendering error messages. This lack of input sanitization allows attackers to inject HTML or JavaScript code that executes in the context of legitimate users' browsers. The vulnerability is classified as a classic XSS flaw that can be categorized under CWE-79, which specifically addresses Cross-Site Scripting vulnerabilities in software applications.
The operational impact of CVE-2010-2477 extends beyond simple script injection, as it can enable attackers to perform session hijacking, deface web applications, steal user credentials, or redirect victims to malicious sites. When exploited, the vulnerability allows remote attackers to execute arbitrary web scripts in the context of the victim's browser session, potentially compromising user data and application integrity. The scope of impact is broad since Paste is a widely used Python web framework component that serves as a foundation for many web applications. Attackers can leverage this vulnerability to manipulate error pages that are often displayed to users when they encounter broken links or invalid URLs, making the attack surface particularly extensive. The vulnerability is particularly dangerous in environments where users have privileged access to applications, as it could enable privilege escalation attacks through session manipulation.
Mitigation strategies for CVE-2010-2477 require immediate patching of affected Paste framework versions to 1.7.4 or later, where proper input sanitization has been implemented. Organizations should also implement comprehensive input validation at multiple layers of their web applications, including application-level sanitization of user-supplied URLs and paths before they reach the framework's error handling components. The implementation of Content Security Policy headers can provide additional defense-in-depth measures by restricting script execution and preventing unauthorized code injection. Security teams should also conduct thorough vulnerability assessments of all web applications using Paste to identify potential custom implementations that might be vulnerable to similar XSS patterns. From an ATT&CK framework perspective, this vulnerability maps to T1566.001 (Phishing: Spearphishing Attachment) and T1059.007 (Command and Scripting Interpreter: JavaScript) as attackers can use the XSS to deliver malicious payloads and execute JavaScript in victim browsers. Organizations should also consider implementing web application firewalls to detect and block suspicious URL patterns that might indicate attempted exploitation of this vulnerability.