CVE-2018-0499 in xapian-core
Summary
by MITRE
A cross-site scripting vulnerability in queryparser/termgenerator_internal.cc in Xapian xapian-core before 1.4.6 exists due to incomplete HTML escaping by Xapian::MSet::snippet().
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Analysis
by VulDB Data Team • 03/29/2023
The vulnerability identified as CVE-2018-0499 represents a significant cross-site scripting flaw within the Xapian search library ecosystem, specifically affecting versions prior to 1.4.6. This issue resides in the queryparser/termgenerator_internal.cc file and manifests through the Xapian::MSet::snippet() method which fails to properly escape HTML characters in search results. The flaw occurs when user-supplied input containing malicious script code is processed through Xapian's search functionality and subsequently rendered in web interfaces without adequate sanitization. This vulnerability directly impacts web applications that utilize Xapian for search operations and display search results to end users, creating a potential attack vector for malicious actors to inject and execute arbitrary JavaScript code within victim browsers. The vulnerability classification aligns with CWE-79 which specifically addresses Cross-Site Scripting flaws, and can be mapped to ATT&CK technique T1566.001 for initial access through malicious web content. The root cause stems from incomplete HTML escaping mechanisms that fail to properly encode special characters such as angle brackets, quotes, and ampersands that are commonly used in XSS attack payloads. When search queries contain these characters, the snippet generation process does not sufficiently sanitize the output before presentation to users, allowing attackers to craft search terms that, when displayed in search results, execute malicious scripts in the context of the victim's browser.
The operational impact of this vulnerability extends beyond simple data theft or defacement scenarios, as it enables attackers to establish persistent access through session hijacking, credential theft, or redirection to malicious sites. Web applications using Xapian for search functionality become vulnerable to attacks where malicious users can inject script code through search queries that gets executed when other users view search results or snippets. The vulnerability is particularly dangerous in environments where search functionality is exposed to untrusted users, such as public forums, e-commerce platforms, or content management systems that rely on Xapian for indexing and search operations. Attackers can exploit this weakness by crafting search terms containing malicious payloads that, when processed by the vulnerable Xapian::MSet::snippet() method, execute in the browser context of any user who views the affected search results. The implications include potential data exfiltration, unauthorized access to user accounts, and the ability to perform actions on behalf of users within the application's security context. This vulnerability demonstrates the critical importance of input validation and output encoding in search and indexing libraries, particularly those used in web applications where user input directly influences displayed content. The vulnerability's exploitation requires minimal technical skill and can be automated, making it a particularly attractive target for mass exploitation campaigns.
Mitigation strategies for CVE-2018-0499 focus primarily on upgrading to Xapian core version 1.4.6 or later, where the HTML escaping mechanisms have been properly implemented to address the incomplete sanitization issue. Organizations should conduct comprehensive vulnerability assessments to identify all applications utilizing affected versions of Xapian and prioritize patching efforts accordingly. Additional defensive measures include implementing Content Security Policy headers to limit script execution, employing web application firewalls that can detect and block suspicious search queries, and conducting regular security audits of search functionality. The fix implemented in version 1.4.6 addresses the underlying issue by ensuring proper HTML escaping of special characters in the snippet generation process, preventing malicious script code from being executed when search results are displayed. Security teams should also consider implementing input validation for search queries to detect potentially malicious payloads before they are processed by the Xapian library. Regular monitoring of security advisories for Xapian and related components is essential to maintain awareness of similar vulnerabilities that may affect the broader search infrastructure. The vulnerability serves as a reminder of the critical need for robust output encoding practices in search libraries and the importance of thorough security testing for components that handle user-generated content in web applications. Organizations should also implement proper logging and monitoring of search activities to detect potential exploitation attempts and maintain audit trails for security incident response.