CVE-2018-25334: Zechat 1.5 CSRF Vulnerability

CVE-2018-25334 Overview

CVE-2018-25334 is a Cross-Site Request Forgery (CSRF) vulnerability [CWE-352] in Zechat 1.5, a chat application built on the ByLancer platform. The application implements a CSRF token, but attackers can bypass this protection by injecting an encoded payload through the hashtag parameter. Successful exploitation lets an unauthenticated attacker modify a victim's account information when the victim visits a crafted page or submits an attacker-controlled form. The flaw stems from improper validation of the anti-CSRF token in conjunction with the hashtag input.

Critical Impact

An attacker who tricks an authenticated Zechat user into loading a crafted page can change that user's profile data without consent, undermining account integrity.

Affected Products

• Zechat 1.5 (ByLancer)
• Deployments using the unpatched CSRF token validation logic
• Web instances exposing the hashtag parameter to untrusted input

Discovery Timeline

• 2026-05-17 - CVE-2018-25334 published to NVD
• 2026-05-18 - Last updated in NVD database

Technical Details for CVE-2018-25334

Vulnerability Analysis

The vulnerability is a CSRF token bypass affecting Zechat 1.5's user information update workflow. The application generates a CSRF token to protect state-changing requests, but the validation routine does not adequately bind that token to the request context. An attacker can read or set the CSRF token through the hashtag parameter using an encoded payload, allowing forged requests to pass server-side checks. Once the protection is bypassed, the attacker can submit profile-modification requests on behalf of any authenticated victim who interacts with the malicious content.

Root Cause

The root cause is improper anti-CSRF token handling [CWE-352]. The Zechat 1.5 endpoint accepts a CSRF token sourced from the hashtag parameter and treats an encoded value as valid without verifying its origin against the user's authenticated session. This permits an attacker to satisfy the token check using a value they control or can predict, breaking the same-origin assumption the protection is designed to enforce.

Attack Vector

Exploitation occurs over the network and requires user interaction. The attacker hosts a crafted page or form that targets the Zechat user-update endpoint and embeds an encoded CSRF payload in the hashtag parameter. When an authenticated victim visits the page, the browser submits the forged request along with the victim's session cookies. A JavaScript-based variant can first fetch the CSRF token, then issue the malicious update request to automate the bypass. Technical proof-of-concept details are available in Exploit-DB #44685 and the VulnCheck CSRF Advisory.

Detection Methods for CVE-2018-25334

Indicators of Compromise

• Unexpected profile changes (email, password, display name) on Zechat user accounts without corresponding user-initiated sessions.
• HTTP requests to Zechat update endpoints containing an encoded value in the hashtag parameter sourced from an external Referer.
• Multiple profile-update requests originating from the same browser session shortly after a victim visits a third-party URL.

Detection Strategies

• Inspect web server and WAF logs for POST requests to user-update endpoints where the Referer header is absent or points to an untrusted domain.
• Alert on requests where the CSRF token value appears to be supplied through the hashtag query parameter rather than the standard form field.
• Correlate profile change events with user activity logs to identify changes that lack a preceding authenticated UI session.

Monitoring Recommendations

• Enable verbose logging on Zechat account modification endpoints and forward events to a centralized log platform for retention and analysis.
• Monitor outbound user reports for unauthorized account changes and tie them back to request logs for forensic review.
• Track anomalous spikes in profile-update traffic from a single IP range or User-Agent consistent with automated CSRF exploitation.

How to Mitigate CVE-2018-25334

Immediate Actions Required

• Restrict access to Zechat 1.5 administrative and profile-update endpoints behind a WAF rule that rejects requests carrying CSRF tokens in the hashtag parameter.
• Force re-authentication for sensitive profile changes such as email address and password updates.
• Audit user accounts for unauthorized modifications since the deployment of Zechat 1.5.

Patch Information

No vendor-supplied patch is referenced in the available advisories for Zechat 1.5. Operators should contact the vendor through the ByLancer Platform Overview for an updated release or deprecation guidance. Where a fixed build is unavailable, apply the workarounds below and consider migrating to a supported chat platform.

Workarounds

• Enforce the SameSite=Strict attribute on session cookies to block cross-origin submission of authenticated requests.
• Validate the Origin and Referer headers on all state-changing endpoints and reject requests that do not match the application's own domain.
• Bind CSRF tokens to the user session server-side and reject any token supplied through query parameters such as hashtag.
• Require a re-authentication step or out-of-band confirmation for profile changes until a vendor fix is available.

# Example nginx rule to block CSRF token smuggling via the hashtag parameter
if ($args ~* "(^|&)hashtag=") {
    return 403;
}