CVE-2026-119407 in Web
Summary
by MITRE • 10/30/2026
Element Web and Element Desktop before 1.12.32 accept guest credentials from URL fragment parameters in loadSession, allowing remote unauthenticated attackers to log out users and clear local stores. Attackers can lure logged-in users into opening links with guest_user_id and guest_access_token to force an attacker-controlled guest session and destroy unbacked end-to-end encryption keys.
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Analysis
by VulDB Data Team • 10/30/2026
The vulnerability identified in Element Web and Element Desktop prior to version 1.12.32 represents a critical authentication bypass mechanism rooted in the improper handling of URL fragment parameters during the session loading process. Specifically, the loadSession function accepts guest credentials provided via the URL fragment without sufficient validation or isolation checks against existing authenticated sessions. This architectural flaw allows remote unauthenticated attackers to inject malicious links containing specific query parameters such as guest_user_id and guest_access_token. When a legitimate user clicks on these crafted URLs, the application processes the embedded guest credentials within the browser's local storage context, effectively overriding the current session state without requiring any form of authentication or explicit user consent beyond clicking the link itself.
From an operational perspective, this vulnerability enables attackers to perform unauthorized logout operations and clear local data stores associated with the victim’s account. The most severe consequence arises from the destruction of unbacked end-to-end encryption keys stored locally on the client device. Since Element relies heavily on client-side key management for secure messaging, losing these keys results in a permanent loss of access to historical encrypted messages that cannot be recovered through server-side backups. This effectively compromises the confidentiality and integrity of past communications, rendering them inaccessible even if the user regains control of their account credentials later. The attack vector is particularly dangerous because it leverages social engineering tactics where victims are lured into visiting malicious links under false pretenses, making detection by traditional security controls difficult.
This vulnerability aligns with CWE-20 Improper Input Validation and CWE-798 Use of Hard-coded Credentials in the context of session management flaws. It also maps to MITRE ATT&CK technique T1534 Internal Spearphishing, as it involves manipulating a user’s environment through deceptive links within an internal or trusted application ecosystem. The exploitation does not require network-level access but rather relies on the victim's interaction with malicious content delivered via external channels such as email, instant messaging platforms, or web pages.
Mitigation strategies must prioritize immediate software updates to version 1.12.32 or later where this logic has been corrected to prevent guest credentials from overriding active sessions. Administrators should enforce strict Content Security Policy headers and implement link sanitization mechanisms within any integrated communication channels that might relay such URLs. Additionally, users are advised to enable end-to-end encryption key backup features provided by the platform whenever available, ensuring that cryptographic material is not solely dependent on local device storage which can be wiped or corrupted through this type of session hijacking attack. Regular security awareness training should also be conducted to help users recognize and avoid clicking suspicious links containing unusual URL parameters in trusted applications.