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Roundcube Webmail has fixed a critical security flaw that could enable remote code execution after authentication. Disclosed by security researcher firs0v, the issue has been addressed in the latest updates for the 1.6 and 1.5 LTS versions.
The security update addresses a post-authentication RCE vulnerability caused by PHP object deserialization. This flaw allows an attacker with valid credentials or access to an authenticated session to execute arbitrary PHP code on the server, threatening data integrity and server control.
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“Fix Post-Auth RCE via PHP Object Deserialization reported by firs0v,” reads the changelog entry, marking the vulnerability as a high-priority issue in the latest releases.
Deserialization vulnerabilities happen when user input is processed by PHP’s unserialize() function without proper validation. This allows attackers to create payloads that cause harmful behavior.
Roundcube Webmail is widely used by individuals, hosting providers, and businesses. Its extensive use and interaction with email data mean that a server-side RCE vulnerability, even after authentication, could enable attackers to:
Deploy web shells
Access or alter emails and user data
Use compromised servers for further internal intrusion or spam campaigns
The vulnerability impacts both:
Roundcube 1.6.x
Roundcube 1.5.x (LTS)
Users are urged to upgrade to the latest versions:
1.6.11
1.5.10
These versions also include numerous bug fixes, including improvements to OAuth token refresh, HTML message previews, dark mode rendering, and support for ldapi:// URIs.
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