Description
An XSS issue was discovered in Horde Groupware Webmail Edition through 5.2.22 (where the Horde_Text_Filter library before 2.3.7 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.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 12 | php-horde-text-filter | 2.3.7-1 | — |
| Debian 9 | php-horde-text-filter | 2.3.5-1+deb9u1 | DLA-2564-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | php-horde-text-filter | No fix yet | — |
| Ubuntu 16.04 LTS | php-horde-text-filter | No fix yet | — |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Exploit-DB 1
- Horde Groupware Webmail 5.2.22 - Stored XSS EDB-49769 · webapps · Apr 15, 2021
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 1
- DLA-2564-1 php-horde-text-filter - security update Debian Security (DSA / DLA) · Mar 9, 2026
References
- https://github.com/horde/webmail/releases
- https://www.horde.org/apps/webmail
- https://www.alexbirnberg.com/horde-xss.html
- https://lists.horde.org/archives/announce/2021/001298.html
- [debian-lts-announce] 20210219 [SECURITY] [DLA 2564-1] php-horde-text-filter security update mailing-list
- http://packetstormsecurity.com/files/162187/Webmail-Edition-5.2.22-XSS-Remote-Code-Execution.html
- http://packetstormsecurity.com/files/162194/Horde-Groupware-Webmail-5.2.22-Cross-Site-Scripting.html