CVE-2022-23656 in Zulip
Summary
by MITRE • 03/03/2022
Zulip is an open source team chat app. The `main` development branch of Zulip Server from June 2021 and later is vulnerable to a cross-site scripting vulnerability on the recent topics page. An attacker could maliciously craft a full name for their account and send messages to a topic with several participants; a victim who then opens an overflow tooltip including this full name on the recent topics page could trigger execution of JavaScript code controlled by the attacker. Users running a Zulip server from the main branch should upgrade from main (2022-03-01 or later) again to deploy this fix.
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Analysis
by VulDB Data Team • 03/04/2022
The vulnerability identified as CVE-2022-23656 affects Zulip Server versions from the main development branch released after June 2021, presenting a cross-site scripting flaw on the recent topics page. This vulnerability stems from insufficient input validation and sanitization of user-provided full names within the application's tooltip functionality. The security flaw exists in the way the system handles user account data when rendering overflow tooltips, creating an opportunity for malicious code execution through crafted user profiles. The vulnerability specifically impacts the recent topics page where tooltip elements display user full names, making it a client-side execution vector that requires user interaction to exploit.
The technical implementation of this vulnerability involves the improper handling of HTML content within tooltip elements that display user full names. When an attacker registers an account with a maliciously crafted full name containing JavaScript code, and subsequently posts messages to topics with multiple participants, the malicious code becomes embedded within the tooltip rendering process. The vulnerability is classified as a CWE-79 Improper Neutralization of Input During Web Page Generation, which represents one of the most common and dangerous web application security flaws. This weakness allows attackers to inject malicious scripts that execute in the context of the victim's browser session, potentially leading to session hijacking, data theft, or further exploitation of the compromised system.
The operational impact of this vulnerability extends beyond simple script execution as it represents a sophisticated attack vector that requires minimal user interaction to be effective. Victims only need to open the overflow tooltip on the recent topics page to trigger the malicious JavaScript execution, making it particularly dangerous in collaborative environments where users frequently interact with multiple topics and participants. The vulnerability affects all users who have access to the recent topics page and are logged into the Zulip Server, potentially compromising entire teams or organizations that rely on the platform for communication. This type of vulnerability aligns with ATT&CK technique T1566.001 Phishing, as it leverages social engineering through the natural user behavior of opening tooltips to view participant information, making the attack more likely to succeed than traditional methods requiring explicit user action.
Organizations running Zulip Server from the main development branch should immediately upgrade to versions released after March 1, 2022, to address this vulnerability. The recommended mitigation strategy involves implementing proper input sanitization and output encoding for all user-provided data, particularly in tooltip and display contexts. The fix should ensure that any HTML content within user full names is properly escaped or sanitized before rendering in the browser, preventing script execution through the tooltip functionality. Additionally, organizations should consider implementing Content Security Policy headers to provide an additional layer of protection against cross-site scripting attacks, and conduct regular security audits of user input handling mechanisms to identify potential similar vulnerabilities in other parts of the application.