A vulnerability was found in Genexis GAPS up to 7.2. It has been classified as critical. This affects some unknown processing of the component CPE Command Handler. The manipulation with an unknown input leads to a information disclosure vulnerability. CWE is classifying the issue as CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. This is going to have an impact on confidentiality, and integrity. The summary by CVE is:

CPEs used by subscribers on the access network receive their individual configuration settings from a central GAPS instance. A CPE identifies itself by the MAC address of its WAN interface and a certain "chk" value (48bit) derived from the MAC. The algorithm used to compute the "chk" was disclosed by reverse engineering the CPE's firmware. As a result, it is possible to forge valid "chk" values for any given MAC address and therefore receive the configuration settings of other subscribers' CPEs. The configuration settings often contain sensitive values, for example credentials (username/password) for VoIP services. This issue affects Genexis B.V. GAPS up to 7.2.

The bug was discovered 01/13/2017. The weakness was shared 12/18/2017 by Antoine Neuenschwander (ant0inet) with CSNC as Genexis GAPS Access Control Vulnerability as confirmed mailinglist post (Full-Disclosure). The advisory is shared at seclists.org. The vendor cooperated in the coordination of the public release. This vulnerability is uniquely identified as CVE-2017-6094 since 02/18/2017. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are unknown but a public exploit is available. MITRE ATT&CK project uses the attack technique T1592 for this issue.

A public exploit has been developed by Antoine Neuenschwander (ant0inet) and been published 2 days after the advisory. The exploit is shared for download at seclists.org. It is declared as proof-of-concept. The vulnerability was handled as a non-public zero-day exploit for at least 339 days. During that time the estimated underground price was around $0-$5k. The code used by the exploit is:

def chk(mac):
    a = [int(x, 16) for x in mac.split(':', 6)]
    chk = [0] * 6

    chk[5] = 1*a[0] + 3*a[1] + 7*a[2]                            + 115 & 0xff
    chk[3] =          7*a[1] + 1*a[2] + 3*a[3]                   + 101 & 0xff
    chk[0] =                   3*a[2] + 7*a[3] + 1*a[4]          +  99 & 0xff
    chk[4] =                            1*a[3] + 3*a[4] + 7*a[5] + 114 & 0xff
    chk[1] = 3*a[0]                            + 7*a[4] + 1*a[5] + 101 & 0xff
    chk[2] = 7*a[0] + 1*a[1]                            + 3*a[5] + 116 & 0xff

    return ':'.join(['{:02x}'.format(x) for x in chk])

Upgrading to version 6.2 or 7.3 eliminates this vulnerability. A possible mitigation has been published immediately after the disclosure of the vulnerability.

Further details are available at twitter.com.

Productinfo

Vendor

• Genexis

Name

• GAPS

Version

• 7.0
• 7.1
• 7.2

CPE 2.3info

• 🔍
• 🔍
• 🔍

CPE 2.2info

• 🔍
• 🔍
• 🔍

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Discussion