CVE-2012-6112 in Spellchecker Php
Summary
by MITRE
classes/GoogleSpell.php in the PHP Spellchecker (aka Google Spellchecker) addon before 2.0.6.1 for TinyMCE, as used in Moodle 2.1.x before 2.1.10, 2.2.x before 2.2.7, 2.3.x before 2.3.4, and 2.4.x before 2.4.1 and other products, does not properly handle control characters, which allows remote attackers to trigger arbitrary outbound HTTP requests via a crafted string.
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Analysis
by VulDB Data Team • 12/21/2021
The vulnerability identified as CVE-2012-6112 resides within the GoogleSpell.php file of the PHP Spellchecker addon for TinyMCE, a widely used rich text editor component. This flaw affects Moodle versions up to 2.4.0 and numerous other applications that integrate this spellchecking functionality. The vulnerability stems from inadequate input validation and sanitization mechanisms within the spellchecker's implementation, specifically concerning how it processes control characters in user-provided strings. The affected component fails to properly sanitize or filter input before constructing outbound HTTP requests, creating a pathway for malicious exploitation.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious string containing control characters that are not properly handled by the spellchecker module. These unfiltered control characters can be interpreted by the underlying HTTP client library or network stack, allowing the spellchecker to initiate arbitrary outbound HTTP requests to attacker-controlled servers. The vulnerability specifically targets the spellchecker's communication mechanism with Google's spell checking service, where the malformed input is passed through to external services without proper validation. This represents a classic case of improper input handling that can lead to unintended network communication and potential data exfiltration or command execution.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables remote attackers to perform unauthorized outbound network communications from systems running vulnerable applications. In the context of Moodle, this could allow attackers to exfiltrate sensitive user data, credentials, or system information to external attacker-controlled servers. The vulnerability is particularly concerning because it operates at the spellchecking layer, which is frequently used by end users, making exploitation relatively straightforward. Security researchers have classified this issue under CWE-20, which deals with improper input validation, and it aligns with ATT&CK techniques involving command and control communications and data exfiltration through network protocols.
Mitigation strategies for this vulnerability require immediate patching of affected software versions to the patched releases mentioned in the CVE description. Organizations should ensure all instances of Moodle and other affected applications are updated to versions containing the security fix. Additionally, network-level controls should be implemented to monitor and restrict outbound HTTP traffic from web servers, particularly to suspicious or unauthorized domains. Input sanitization measures should be enhanced at multiple layers, including application-level filtering of control characters and implementing proper HTTP request validation. Security teams should also consider implementing web application firewalls to detect and block malicious requests that attempt to exploit this vulnerability. The remediation process should include comprehensive testing to ensure that the patch does not introduce regressions in spellchecking functionality while maintaining the security improvements.