SEC Consult Vulnerability Lab Security Advisory < 20231205-0 >  
title: Argument injection leading to unauthenticated RCE and  
authentication bypass  
product: Atos Unify OpenScape Session Border Controller (SBC)  
Atos Unify OpenScape Branch  
Atos Unify OpenScape BCF  
vulnerable version: OpenScape SBC before V10 R3.4.0  
OpenScape Branch before V10 R3.4.0  
OpenScape BCF V10 before V10 R10.12.00 and V10 R11.05.02  
fixed version: OpenScape SBC V10 R3.4.0 or higher  
OpenScape Branch V10 R3.4.0 or higher  
OpenScape BCF V10 R10.12.00 or higher, V10 R11.05.02  
CVE number: CVE-2023-6269  
impact: Critical  
found: 2023-09-01  
by: Armin Weihbold (Office Linz)  
SEC Consult Vulnerability Lab  
An integrated part of SEC Consult, an Eviden business  
Europe | Asia  
Vendor description:  
"Unify is is the Atos brand for communication and collaboration solutions  
Unify is the newest member of the Atos family, combining Atos’ knowledge and  
reputation in the IT services market with Unify’s expertise in unified  
communications and collaboration to provide customers with seamless services  
solutions for their entire digital portfolio. Within Atos, Unify continues to  
deliver a unique integrated proposition for unified communications and real  
time capabilities."  
Business recommendation:  
SEC Consult recommends users of this solution to immediately install the latest  
patch from the vendor.  
Furthermore, an in-depth security analysis performed by security professionals  
is highly advised, as the software may be affected from other security issues.  
Vulnerability overview/description:  
1) Argument injection leading to unauthenticated RCE and authentication bypass (CVE-2023-6269)  
The administrative web interface insufficiently escapes supplied login  
credentials before passing them to a user management application, leading to  
an unauthenticated attacker being able to gain root access to the appliance  
via SSH.  
Another possibility to exploit this vulnerability is to append a special  
argument during logon to completely bypass the authentication of the web interface.  
A previously unauthenticated attacker can logon as administrator without any  
known credentials.  
Proof of concept:  
1) Argument injection leading to unauthenticated RCE and authentication bypass (CVE-2023-6269)  
Example 1) Gaining unauthenticated SSH root access  
The file receiving data from the login page is `auth.php`, here the  
user-provided credentials are passed on to the function  
`PasswordMgr::authPassword` after some checks on the supplied username.  
// /srv/www/htdocs/auth.php  
// [...]  
$error = '';  
// [...]  
if( !sessionLimitReached() )  
// Authenticate user/password...  
$privilege = PasswordMgr::getUserPrivilege($local_user);  
if (($local_user == 'assistant') || ($local_user == 'cdr') || (!PasswordMgr::isUserEnabled($local_user))){  
$ret = false;  
else {  
switch ($privilege) {  
case 'admin':  
$ret = PasswordMgr::authPassword($_POST["username"], $_POST["password"], $error, $real_user, $local_user, FALSE);  
// [...]  
// [...]  
// [...]  
The function `PasswordMgr::authPassword` in `core/PasswordMgr.php` is just a  
wrapper around `call_osbpasswd` in the same file.  
// /srv/www/htdocs/core/PasswordMgr.php  
public static function authPassword($username, $password, &$error, &$real_user, &$local_user, $local = FALSE)  
if ( PasswordMgr::call_osbpasswd("auth", $username, $password, $error, $real_user, $local_user, $local ) )  
$error='Current Password does not match user';  
return false;  
return true;  
The function `call_osbpasswd` is responsible for anything related to user  
management, it does this by constructing shell arguments and supplying them to  
the executable `/osb/bin/osbpasswd` which is executed with root privileges via  
`cfgUtilExecSudo`. This executable handles the actual authentication, creation  
of users, and other tasks.  
In the case of authentication the arguments are written to a temporary file  
and read from there.  
Before that the supplied password is escaped using `escapeshellcmd` instead of  
`escapeshellarg`. This means that space characters (hex 0x20) in the password  
are left intact allowing for argument injection.  
// /srv/www/htdocs/core/PasswordMgr.php  
public static function call_osbpasswd( $method, $username, $password, &$output, &$real_user, &$local_user, $local, $extraArg = '' )  
// [...]  
$curruser = 'GUI';  
// [...]  
$params = "$method";  
if ($local) $params .= ' --local';  
if ($username != '') $params .= " --user $username";  
if ($curruser != '') $params .= " --curruser $curruser";  
if ($extraArg != '') $params .= "$extraArg";  
$file = '';  
// [...]  
else {  
$params .= " --password ";  
$fakePar = $params."xxxxxx";  
$params .= escapeshellcmd($password);  
$params .= "\n";  
$file = tempnam('/osb/var/tmp','osbpasswd.'.md5($params).'.');  
/*E.g.: /opt/openbranch/var/tmp/osbpasswd.f9e2a9fcf29c6275830257316d560e27.CG4IcQ */  
cfgUtilEcho( $params, $file );  
$command = "/osb/bin/osbpasswd ".$fakePar." --file ".$file;  
$outArray = array();  
$ret = cfgUtilExecSudo($command, $outArray, FALSE, TRUE);  
// [...]  
return $ret;  
The function that is responsible for parsing command line arguments  
in the called application `/osb/bin/osbpasswd` iterates over arguments and  
sets global variables based on them. This is done in a loop and no check is  
done if that argument was already set. This means an attacker can override all  
parameters by specifying them again.  
int parse_arguments(int argc, char **argv, int n)  
// [...]  
while ( n < argc && argv[n] ) {  
// [...]  
else if ( !strcmp("--user", argv[n]) ) {  
if ( ++n < argc )  
arg_user = argv[n];  
else if ( !strcmp("--shell", argv[n]) ) {  
if ( ++n < argc )  
arg_shell = argv[n];  
// [...]  
else if ( !strcmp("auth", argv[n]) ) {  
arg_command_name = argv[n];  
arg_command_number = 1;  
else if ( !strcmp("add", argv[n]) ) {  
arg_command_name = argv[n];  
arg_command_number = 6;  
// [...]  
return 0LL;  
The combination of faulty escaping of the supplied password and overly  
permissive parsing of arguments in the called binary leads to an attacker being  
able to request arbitrary operations from the `/osb/bin/osbpasswd` binary with  
arbitrary arguments. An attacker could for example create a new user with SSH  
access and change the password of the root user leading to a complete  
compromise of the system.  
To demonstrate the vulnerability, it is sufficient to [...]  
[ Proof of concept removed ]  
- this creates a new user with SSH access, the second one [...]  
[ Proof of concept removed ]  
which changes the password of the root user. The attacker can then login [...]  
to gain root access.  
Example 2) Bypassing the web interface logon as administrator  
As described in example 1, the same vulnerability can also be exploited to  
bypass the logon for the web interface and immediately gain access as  
administrator because the arguments for the command-line tool are passed and  
By supplying the [...] following [...] string [...], it is possible to logon  
without known credentials:  
[ Proof of concept removed ]  
Afterwards the attacker is logged on as administrator (or any other supplied  
user account).  
Vulnerable / tested versions:  
The following version has been tested which was the latest version available  
at the time of the test:  
* Atos Unify OpenScape Session Border Controler (SBC) Firmware Version V10 R3.3.0  
According to vendor, versions before V10 R3.3.0 are affected as well.  
The vendor confirmed that the following products are vulnerable:  
* Atos Unify OpenScape SBC V10 before V10 R3.4.0  
* Atos Unify OpenScape Branch V10 before V10 R3.4.0  
* Atos Unify OpenScape BCF V10 before V10R10.12.00 and V10R11.05.02  
Vendor contact timeline:  
2023-09-13: Contacting vendor through email; sending  
encrypted advisory (S/MIME)  
2023-09-25: Call with vendor, patch has already been developed, available  
internally for testing & QA since 22nd.  
2023-09-26: Preliminary vendor security advisory available, giving feedback  
regarding recommendations. Vendor informs customers in advance  
(TLP:AMBER), patch planned for 2023-09-27.  
2023-10-04: Vendor security advisory public release (TLP:WHITE).  
2023-10-06: Asking regarding next steps for affected product Atos Unify  
OpenScape BCF.  
2023-10-10: Vendor confirms that OpenScape BCF is affected as well and added  
it to their advisory.  
2023-11-27: Reserving CVE-2023-6269 and sending it to vendor, defining  
release date of 5th December.  
2023-12-05: Coordinated release of security advisory.  
The vendor provides a patch for the affected products:  
* Atos Unify OpenScape Session Border Controller Firmware Version V10 >=R3.4.0  
* Atos Unify OpenScape Branch version V10 >=R3.4.0  
* Atos Unify OpenScape BCF version V10 >=V10R10.12.00 and V10R11.05.02  
The patches can be obtained for registered customers through the vendor's  
download server: or via  
Furthermore, the vendor has also released a security advisory which is  
available here:  
In addition to deploying the patch, limit access to the administrative  
web application and SSH ports to authorized personnel on the network level.  
Advisory URL:  
SEC Consult Vulnerability Lab  
An integrated part of SEC Consult, an Eviden business  
Europe | Asia  
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EOF A. Weihbold / @2023