Debian Security Advisory

DLA-2564-1 php-horde-text-filter -- LTS security update

Date Reported:
18 Feb 2021
Affected Packages:
Security database references:
In the Debian bugtracking system: Bug 982769.
In Mitre's CVE dictionary: CVE-2021-26929.
More information:

Alex Birnberg discovered a cross-site scripting (XSS) vulnerability in the Horde Application Framework, more precisely its Text Filter API. An attacker could take control of a user's mailbox by sending a crafted e-mail.

  • CVE-2021-26929

    An XSS issue was discovered in Horde Groupware Webmail Edition (where the Horde_Text_Filter library is used). The attacker can send a plain text e-mail message, with JavaScript encoded as a link or email that is mishandled by preProcess in Text2html.php, because bespoke use of \x00\x00\x00 and \x01\x01\x01 interferes with XSS defenses.

For Debian 9 stretch, this problem has been fixed in version 2.3.5-1+deb9u1.

We recommend that you upgrade your php-horde-text-filter packages.

For the detailed security status of php-horde-text-filter please refer to its security tracker page at:

Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: