Username Spoofing in Roundcube Webmail

Executive Summary

CVE-2026-62644 is a vulnerability in Roundcube Webmail versions before 1.6.17 and 1.7.x before 1.7.2. The issue affects the password plugin, which was vulnerable to username spoofing via session data.

An attacker could manipulate session data to inject a malicious username, leading to account takeover. The vulnerability arises because the password plugin previously relied on session-stored usernames without proper validation or sanitization, allowing unauthorized access to user accounts.

• The vulnerability is classified under CVSS v3.1 with a BaseScore of 6.4, indicating a medium severity level.
• The attack vector is network-based (AV:N), requires low privileges (PR:L), and user interaction (UI:R).
• The impact includes high confidentiality (C:H) and integrity (I:H) risks, but no availability impact (A:N).

Useful 0 Not Useful 0

Detection Guidance

Detecting this vulnerability requires checking if your Roundcube Webmail instance is running a vulnerable version (before 1.6.17 or 1.7.x before 1.7.2). You can verify the installed version by accessing the Roundcube Webmail interface or checking the version file in the installation directory.

• Check the Roundcube version via the command line: cat /path/to/roundcube/program/include/iniset.php | grep RCMAIL_VERSION. Replace /path/to/roundcube with your actual installation path.
• Inspect the Roundcube logs for unusual session activity or failed login attempts that may indicate exploitation attempts. Look for logs in /var/log/roundcube/ or the configured log directory.
• Review the password plugin configuration files (e.g., config.inc.php) for any unauthorized changes, particularly in the LDAP or SQL driver settings.

Network-level detection may involve monitoring for unusual LDAP or SQL queries originating from the Roundcube server, which could indicate an attempt to exploit the session-injected username vulnerability.

Useful 0 Not Useful 0

Impact Analysis

If you are using an affected version of Roundcube Webmail (before 1.6.17 or 1.7.x before 1.7.2), this vulnerability could allow an attacker to take over your account.

• An attacker could manipulate session data to impersonate your username, gaining unauthorized access to your emails and account settings.
• This could lead to sensitive information disclosure, such as reading or sending emails on your behalf.
• The attacker could also change your account password or other settings, locking you out of your own account.

The vulnerability is particularly risky in environments where Roundcube Webmail is used for business or organizational communication, as it could lead to broader security breaches.

Useful 0 Not Useful 0

Compliance Impact

This vulnerability could have significant implications for compliance with data protection and privacy regulations.

• GDPR (General Data Protection Regulation): If Roundcube Webmail is used to handle personal data of EU citizens, this vulnerability could lead to unauthorized access to such data, violating GDPR's requirements for data protection and confidentiality. Organizations may face fines or legal action if they fail to patch the vulnerability and a breach occurs.
• HIPAA (Health Insurance Portability and Accountability Act): For healthcare organizations using Roundcube Webmail to communicate protected health information (PHI), this vulnerability could result in unauthorized access to PHI, leading to non-compliance with HIPAA's security and privacy rules. This could result in penalties and reputational damage.
• Other standards (e.g., ISO 27001, NIST): The vulnerability undermines security controls related to access management and session security, which are critical components of these frameworks. Failure to address the vulnerability could result in non-compliance during audits.

Organizations should promptly update to the patched versions of Roundcube Webmail to mitigate risks and maintain compliance with applicable regulations.

Useful 0 Not Useful 0

Mitigation Strategies

The most effective mitigation is to upgrade Roundcube Webmail to a patched version (1.6.17 or 1.7.2 and later). If upgrading is not immediately possible, apply the following steps to reduce risk.

• Upgrade Roundcube Webmail to version 1.6.17 or 1.7.2, which includes the fix for CVE-2026-62644. Follow the official upgrade instructions from the Roundcube documentation.
• If upgrading is not feasible, manually apply the patches from the provided commits (Resource 2 and Resource 3) to your Roundcube installation. Focus on modifying the password driver files to pass the username as a parameter instead of relying on session data.
• Disable the password plugin temporarily if it is not critical to your operations. This can be done by removing or renaming the plugin directory (e.g., /path/to/roundcube/plugins/password).
• Monitor Roundcube logs for suspicious activity, such as unexpected LDAP or SQL queries, and investigate any anomalies.
• Restrict access to the Roundcube Webmail interface using network-level controls (e.g., firewalls, IP whitelisting) to limit exposure to potential attackers.
• Ensure that all user sessions are properly invalidated after logout or timeout to reduce the risk of session hijacking.

Useful 0 Not Useful 0