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             AUSCERT External Security Bulletin Redistribution

         TYPO3-CORE-SA-2016-013: Missing Access Check in TYPO3 CMS
                                25 May 2016


        AusCERT Security Bulletin Summary

Product:           TYPO3
Publisher:         TYPO3
Operating System:  UNIX variants (UNIX, Linux, OSX)
Impact/Access:     Execute Arbitrary Code/Commands -- Existing Account
Resolution:        Patch/Upgrade

Original Bulletin: 

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TYPO3-CORE-SA-2016-013: Missing Access Check in TYPO3 CMS

May 24, 2016

Category: TYPO3 CMS

Author: Helmut Hummel

Keywords: Missing Access Check, Extbase

It has been discovered, that TYPO3 CMS lacks an access check for Extbase 

Component Type: TYPO3 CMS

Release Date: May 24, 2016

Vulnerable subcomponent: Extbase

Vulnerability Type: Missing access check

Affected Versions: Versions 4.3.0 up to 8.1.0

Severity: Critical

Suggested CVSS v2.0: AV:N/AC:M/Au:N/C:C/I:C/A:C/E:F/RL:O/RC:C

CVE: not assigned yet

Problem Description: Extbase request handling fails to implement a proper 
access check for requested controller/ action combinations, which makes it 
possible for an attacker to execute arbitrary Extbase actions by crafting a 
special request. To successfully exploit this vulnerability, an attacker must
have access to at least one Extbase plugin or module action in a TYPO3 
installation. The missing access check inevitably leads to information 
disclosure or remote code execution, depending on the action that an attacker
is able to execute.

Solution: Update to TYPO3 versions 6.2.24, 7.6.8 or 8.1.1 that fix the problem

Alternative Solution: Apply the patches suitable for your TYPO3 branch 

Alternative Solution: Download the zip archive which contains a folder with a
script and patches for all affected TYPO3 versions. (Please note: If you were
quick and applied the zip file before the regression was fixed, you need to 
download this undo zip archive, which contains a script to revert the patches.
After running the script, you have to use the script from above to secure your
TYPO3 CMS instances.)

Notes: TYPO3 installations with at least one publicly available Extbase 
action, are exploitable without any further authentication.

TYPO3 installations without publicly available Extbase actions, are still 
exploitable for authenticated backend users with access to a backend module, 
which is based on Extbase.

Important Note: The fix introduced changes in the internal request handling of
Extbase. In case an such unlikely incompatibility with any extension (that 
relies on internal API) occurs, the TYPO3 installation still remains fully 
available and functional, with only little minor issues in Extbase form 
validation handling.

Users of any TYPO3 version from 4.3.0 to 8.1.0 are strongly encouraged to 
upgrade or to at least apply the patches provided below.

Please note, that patching a not supported TYPO3 version can be considered 
only as temporary mitigation. Upgrade to a supported versions should be 
performed as soon as possible.

Credits: Thanks to Stefan Horlacher from Arcus Security GmbH who discovered 
and reported the issue, Alex Kellner, who also reported the issue and Oliver 
Hader for discovering a related vulnerability.

General Advice: Follow the recommendations that are given in the TYPO3 
Security Guide. Please subscribe to the typo3-announce mailing list.

General Note: All security related code changes are tagged so that you can 
easily look them up on our review system.

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