PHP 4.4.4, 5.1.6, and other versions, when running on Apache, allows local users to modify behavior of other sites hosted on the same web server by modifying the mbstring.func_overload setting within .htaccess, which causes this setting to be applied to other virtual hosts on the same server.
The product uses a function that accepts a format string as an argument, but the format string originates from an external source.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Php | Php | 4.4.4 (including) | 4.4.4 (including) |
| Php | Php | 5.1.6 (including) | 5.1.6 (including) |
| Red Hat Enterprise Linux 3 | RedHat | php-0:4.3.2-51.ent | * |
| Red Hat Enterprise Linux 4 | RedHat | php-0:4.3.9-3.22.15 | * |
| Red Hat Enterprise Linux 5 | RedHat | php-0:5.1.6-23.2.el5_3 | * |
| Php5 | Ubuntu | dapper | * |
| Php5 | Ubuntu | devel | * |
| Php5 | Ubuntu | gutsy | * |
| Php5 | Ubuntu | hardy | * |
| Php5 | Ubuntu | intrepid | * |
When an attacker can modify an externally-controlled format string, this can lead to buffer overflows, denial of service, or data representation problems. It should be noted that in some circumstances, such as internationalization, the set of format strings is externally controlled by design. If the source of these format strings is trusted (e.g. only contained in library files that are only modifiable by the system administrator), then the external control might not itself pose a vulnerability.