Skip to content

0-day Vulnerability In Horde Webmail Email System

  • Resources
  • News
  • 0-day Vulnerability In Horde Webmail Email System

We would like to bring your attention to the following 0-day exploit we have recently become aware of.

The Horde Webmail Software has been found to contain a nine year old unpatched security vulnerability. Exploitation of this vulnerability could be used to gain complete access to email accounts simply by previewing an attachment.

Affected Version

5.2.22

The flaw, believed to have been introduced by a code change in November 2012, relates to a stored cross-site scripting flaw (persistent XSS) that allows an attacker to craft an OpenOffice document in such a manner that when it is previewed, it automatically executes an arbitrary JavaScript payload.

The vulnerability triggers when a targeted user views an attached OpenOffice document in the browser. This results in the ability for an attacker to steal all emails the victim has sent and received. If an attacker was successful in targeting an administrator by sending a personalised, malicious email, they could abuse this privileged access to take over the entire webmail server.

Remediation

At this time, there are no patches for Horde webmail that are available, however Horde Webmail users are advised to disable the rendering of OpenOffice attachments by editing the config/mime_drivers.php file to add the ‘disable’ => true configuration option to OpenOffice mime handler.

We are actively monitoring the situation.

References:

City network visual symbolising interconnected systems impacted by the F5 breach

Weaponized patience: the strategic implications of the F5 breach

The F5 breach reveals the growing danger of shared infrastructure attacks. As adversaries learn faster than defenders, the only path to resilience is continuous, adaptive testing.…

Everyone has a plan until they get punched in the face: reflections on the NCSC 2025 annual review

The NCSC Annual Review 2025 delivers a reality check. Highly significant cyber incidents have increased by 50 percent year over year. It’s time to act.
aerial view of a city symbolising complexity and continuous threat readiness

Part 3: CBEST Series – The Future of Threat-Led Penetration Testing

Regulated testing like CBEST is pivotal, but as threats shift, organizations must adopt more strategic, agile threat-led penetration testing. Discover what’s next.