Vigil@nce: Apache httpd, bypassing AllowOverride
June 2009 by Vigil@nce
A local attacker can create a .htaccess file in order to bypass
restrictions of AllowOverride.
Severity: 1/4
Consequences: data reading, data creation/edition
Provenance: user account
Means of attack: no proof of concept, no attack
Ability of attacker: expert (4/4)
Confidence: confirmed by the editor (5/5)
Diffusion of the vulnerable configuration: high (3/3)
Creation date: 16/06/2009
IMPACTED PRODUCTS
– Apache httpd
– Debian Linux
DESCRIPTION OF THE VULNERABILITY
The AllowOverride directive of the Apache httpd configuration file
indicates if directives located in a .htaccess file are honoured.
For example:
AllowOverride None : nothing is allowed
AllowOverride All : everything is allowed
AllowOverride Option : directives changing directory options are
allowed
Since Apache httpd version 2.2, the Option parameter of the
AllowOverride directive can restrict the list of allowed options.
For example:
AllowOverride Options=Indexes,IncludesNOEXEC
However, due to a logic error, when at least one option is
indicated in AllowOverride, they are all allowed (as it was the
case before Apache httpd < 2.2).
An attacker can therefore for example enable the "Includes" option
in a .htaccess file in order to use "#exec cmd" and "#exec cgi"
commands.
CHARACTERISTICS
Identifiers: 44262, DSA 1816-1, VIGILANCE-VUL-8798
http://vigilance.fr/vulnerability/Apache-httpd-bypassing-AllowOverride-8798