CVE-2018-6835 in Etherpad Lite
Summary
by MITRE
node/hooks/express/apicalls.js in Etherpad Lite before v1.6.3 mishandles JSONP, which allows remote attackers to bypass intended access restrictions.
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Analysis
by VulDB Data Team • 02/06/2023
The vulnerability identified as CVE-2018-6835 affects Etherpad Lite versions prior to 1.6.3 and resides within the node/hooks/express/apicalls.js file. This issue represents a critical security flaw that undermines the application's access control mechanisms through improper handling of JSONP requests. The vulnerability enables remote attackers to circumvent intended security restrictions that should normally protect sensitive API endpoints from unauthorized access.
The technical flaw stems from the application's inadequate validation and processing of JSONP (JSON with Padding) requests within its API call handling mechanism. JSONP is a technique used to overcome cross-origin restrictions in web browsers by wrapping JSON responses in a callback function. When improperly implemented, JSONP can create security vulnerabilities where attackers can manipulate the callback parameter to access restricted resources. In this case, the Etherpad Lite application fails to properly validate or sanitize the JSONP callback parameter, allowing malicious actors to construct requests that bypass normal authentication and authorization checks.
The operational impact of this vulnerability is significant as it provides remote attackers with unauthorized access to protected API endpoints within the Etherpad Lite environment. This could potentially allow attackers to retrieve sensitive data, modify content, or perform actions that should be restricted to authenticated users only. The vulnerability affects the core API functionality that governs how external applications and users interact with the Etherpad Lite system, making it a critical concern for any deployment that relies on proper access controls and data protection.
This vulnerability aligns with CWE-284 (Improper Access Control) and represents a classic example of insufficient input validation that leads to privilege escalation or unauthorized data access. From an ATT&CK framework perspective, this issue maps to T1078 (Valid Accounts) and T1046 (Network Service Scanning) as attackers could leverage this flaw to gain access to systems and potentially escalate privileges. The vulnerability also relates to T1566 (Phishing) in scenarios where attackers might use this access to exfiltrate sensitive information or modify collaborative documents.
Organizations using Etherpad Lite should immediately upgrade to version 1.6.3 or later to remediate this vulnerability. Additional mitigations include implementing proper input validation for all JSONP requests, enforcing strict access controls on API endpoints, and monitoring for unusual API access patterns. Security teams should also consider implementing network-level restrictions to limit access to sensitive API endpoints and ensure that proper authentication mechanisms are in place to prevent unauthorized access to collaborative editing features. The fix implemented in version 1.6.3 likely involved strengthening the validation of JSONP callback parameters and ensuring that all API access is properly authenticated and authorized before processing any requests.