Software Engineering Institute

CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer

Dell BIOS in some older Latitude laptops and Precision Mobile Workstations is vulnerable to buffer overflows in the rbu_packet.pktNum and rbu_packet.pktSize values. These values can be set by an attacker while performing an illegitimate BIOS update. The BIOS reads these values when reconstructing the BIOS image, before any signature check occurs.

More information is available from the BIOS Security presentation at Black Hat USA 2013.

By convincing a user with root or administrative privileges to execute a malicious BIOS update, an attacker can bypass the signed BIOS enforcement to install an arbitrary BIOS image that could contain a rootkit or malicious code that persists across operating system re-installations and official BIOS updates.

Apply an Update

Dell has released updated BIOS versions for the affected Latitude and Precision systems that can be downloaded from their support site. Dell has provided the following list of fixed BIOS versions:

Dell System                     Released        Rev
===================================================
Latitude D530                   8/22/2013       A12
Latitude D531                   7/16/2013       A12
Latitude D630                   7/16/2013       A19
Latitude D631                   7/26/2013       A12
Latitude D830                   7/16/2013       A17
Precision M2300                 7/16/2013       A11
Precision M4300                 7/16/2013       A17
Precision M6300                 7/16/2013       A15
Latitude E5400                  7/16/2013       A19
Latitude E5500                  7/16/2013       A19
Latitude E4200                  7/16/2013       A24
Latitude E4300                  7/16/2013       A26
Latitude E6400                  7/16/2013       A34
Latitude E6400 ATG              7/16/2013       A34
Latitude E6400 / ATG / XFR      7/16/2013       A34
Latitude XT2                    7/18/2013       A15
Latitude E6500                  7/16/2013       A29
Latitude Z600                   7/16/2013       A11
Precision M2400                 7/16/2013       A28
Precision M4400                 7/16/2013       A29
Precision M6400                 7/16/2013       A13
Precision M6500                 7/18/2013       A10