CVE-2026-105783 in Joplin
Summary
by MITRE • 10/06/2026
Joplin is an open source note-taking and to-do application that organises notes and lists into notebooks. Prior to 3.7.13, when Joplin Desktop is running with the opt-in Web Clipper server enabled, the server in packages/lib/ClipperServer.ts sends Access-Control-Allow-Origin: * and allows an arbitrary website to call POST /auth and GET /auth/check because the pairing endpoints do not reject HTTP or HTTPS origins. The desktop confirmation dialog does not identify the requesting origin, so a victim who approves the generic prompt authorizes the attacking page, which then receives the permanent API token. The token provides ongoing read and write access to notes, folders, tags, resources, and master keys. This issue is fixed in version 3.7.13.
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Analysis
by VulDB Data Team • 10/06/2026
The vulnerability identified in Joplin Desktop versions prior to 3.7.13 represents a critical authentication bypass and cross-origin resource sharing misconfiguration that compromises the integrity of user data when the optional Web Clipper server is enabled. This component, located within packages/lib/ClipperServer.ts, functions as an HTTP server designed to facilitate communication between web-based clipper extensions and the local desktop application. The core technical flaw lies in the improper implementation of Cross-Origin Resource Sharing policies on specific authentication endpoints. Specifically, the server responds with Access-Control-Allow-Origin: *, a wildcard header that instructs browsers to allow any origin domain to make cross-origin requests to these endpoints without restriction. This configuration effectively disables same-origin policy protections for the pairing and authentication mechanisms, allowing arbitrary websites hosted on the internet to interact directly with the local service running on the victim's machine.
The operational impact of this flaw is severe due to the nature of the data exposed through the API token obtained via these vulnerable endpoints. When a user initiates the pairing process by clicking a link from an attacker-controlled website, Joplin Desktop displays a confirmation dialog requesting permission for the connection. However, this interface fails to display the specific origin or domain name making the request. Consequently, the victim is presented with a generic prompt that lacks contextual information about which external party is seeking access. If the user approves this ambiguous authorization, they inadvertently grant an arbitrary web page permanent API credentials. These credentials provide unrestricted read and write access to sensitive assets including notes, folders, tags, attached resources, and critically, master keys used for encryption. This means an attacker can not only exfiltrate all stored plaintext data but also potentially decrypt previously encrypted content if the master key is compromised or if future synchronization occurs with weak security practices.
From a classification perspective, this vulnerability aligns closely with CWE-942, which describes Cross-Origin Resource Sharing (CORS) misconfiguration allowing unauthorized access to sensitive information. Furthermore, it relates to CWE-798, involving the use of hardcoded credentials or improper authentication mechanisms where session tokens are issued without sufficient verification of the requesting entity's identity. In terms of adversary tactics, this scenario maps to MITRE ATT&CK technique T1503.002, Local Data Staged for Exfiltration via Cross-Origin Requests, as well as aspects of T1078, Valid Accounts, since the attacker obtains legitimate API tokens that mimic authorized user sessions. The lack of origin validation in the pairing flow constitutes a significant failure in input validation and trust boundary enforcement within the desktop application's local server architecture.
Mitigation for this issue requires strict adherence to security best practices regarding CORS implementation and user interface transparency. For users, the immediate remediation is to upgrade Joplin Desktop to version 3.7.13 or later, where the pairing endpoints have been patched to reject HTTP and HTTPS origins that are not explicitly whitelisted or verified against a trusted list of clipper extensions. Developers should ensure that CORS policies are implemented with specific allowlists rather than wildcards for any endpoint handling authentication tokens. Additionally, user interface elements involved in authorization must clearly display the origin domain making the request to prevent social engineering attacks where users cannot distinguish between legitimate and malicious requests. Implementing strict Content Security Policy headers and validating the Origin header against a known set of trusted origins on the server side are essential steps to prevent arbitrary websites from exploiting local services running with elevated privileges or access to sensitive user data.