Advisory Details

This vulnerability allows remote attackers to execute arbitrary code on affected installations of Horde Groupware Webmail Edition. Authentication is required to exploit this vulnerability.

The specific flaw exists within remote_unsubscribe.php. When parsing the remote_cals parameter, the process does not properly validate user-supplied data, which can result in deserialization of untrusted data. An attacker can leverage this vulnerability to execute code in the context of the www-data user.

This vulnerability is being disclosed publicly without a patch in accordance with the ZDI 120 day deadline.

03/13/20 – ZDI reported the vulnerabilities to the vendor
07/07/20 – ZDI requested an update
07/09/20 – The vendor indicated they were working on a fix
07/09/20 – ZDI requested an ETA for the fix
07/09/20 – The vendor indicated that they could not specify a date
07/10/20 – ZDI indicated that it would provide a 2 week extension
07/21/20 – ZDI requested an update
07/31/20 – ZDI requested an update
08/13/20 – ZDI notified the vendor of the intention to publish the case as a 0-day advisory on 08/18/20

-- Mitigation:
Given the nature of the vulnerability the only salient mitigation strategy is to restrict interaction with the application.

• 2020-03-13 - Vulnerability reported to vendor
• 2020-08-19 - Coordinated public release of advisory