OpenVPN NTLM Version 2 Proxy ntlm.c ntlm_phase_3 certificate validation

CVSS Meta Temp Score
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CTI Interest Score
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6.1$0-$5k0.00

Summaryinfo

A vulnerability categorized as problematic has been discovered in OpenVPN. Impacted is the function ntlm_phase_3 of the file ntlm.c of the component NTLM Version 2 Proxy Handler. Executing a manipulation can lead to certificate validation. This vulnerability is tracked as CVE-2017-7520. The attack can be launched remotely. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability has been found in OpenVPN (Network Encryption Software) (affected version unknown) and classified as problematic. This vulnerability affects the function ntlm_phase_3 of the file ntlm.c of the component NTLM Version 2 Proxy Handler. The manipulation with an unknown input leads to a certificate validation vulnerability. The CWE definition for the vulnerability is CWE-295. The product does not validate, or incorrectly validates, a certificate. As an impact it is known to affect availability. CVE summarizes:

OpenVPN versions before 2.4.3 and before 2.3.17 are vulnerable to denial-of-service and/or possibly sensitive memory leak triggered by man-in-the-middle attacker.

The bug was discovered 06/22/2017. The weakness was disclosed 06/21/2017 by Guido Vranken with https://guidovranken.wordpress.com as The OpenVPN post-audit bug bonanza as not defined blog post (Website). The advisory is shared for download at guidovranken.wordpress.com. This vulnerability was named CVE-2017-7520 since 04/05/2017. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1587.003. Responsible for the vulnerability is the following code: 

if (( *((long *)&buf2[0x14]) & 0x00800000) == 0x00800000)          /* Check for Target Information block */
{
    tib_len = buf2[0x28];            /* Get Target Information block size */
    if (tib_len > 96)
    {
        tib_len = 96;
    }
    {
        char *tib_ptr = buf2 + buf2[0x2c];           /* Get Target Information block pointer */
        memcpy(&ntlmv2_blob[0x1c], tib_ptr, tib_len);           /* Copy Target Information block into the blob */
    }
}

The vulnerability scanner Nessus provides a plugin with the ID 101007 (Debian DLA-999-1 : openvpn security update), which helps to determine the existence of the flaw in a target environment. It is assigned to the family Debian Local Security Checks and running in the context l. The commercial vulnerability scanner Qualys is able to test this issue with plugin 196832 (Ubuntu Security Notification for Openvpn Vulnerabilities (USN-3339-1)).

Upgrading eliminates this vulnerability. The upgrade is hosted for download at openvpn.net. A possible mitigation has been published 1 days after the disclosure of the vulnerability.

The vulnerability is also documented in the databases at Tenable (101007) and SecurityFocus (BID 99230†). The entries VDB-102707, VDB-102708, VDB-102709 and VDB-102710 are pretty similar. VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Type

Name

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.3
VulDB Meta Temp Score: 6.2

VulDB Base Score: 5.3
VulDB Temp Score: 5.1
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 7.4
NVD Vector: 🔍

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Certificate validation
CWE: CWE-295 / CWE-287
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Yes

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

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Nessus ID: 101007
Nessus Name: Debian DLA-999-1 : openvpn security update
Nessus File: 🔍
Nessus Risk: 🔍
Nessus Family: 🔍
Nessus Context: 🔍

OpenVAS ID: 867773
OpenVAS Name: Fedora Update for openvpn FEDORA-2017-5596f2f94d
OpenVAS File: 🔍
OpenVAS Family: 🔍

Qualys ID: 🔍
Qualys Name: 🔍

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

Reaction Time: 🔍
0-Day Time: 🔍
Exposure Time: 🔍

Upgrade: openvpn.net

Timelineinfo

04/05/2017 🔍
06/21/2017 +77 days 🔍
06/21/2017 +0 days 🔍
06/22/2017 +1 days 🔍
06/22/2017 +0 days 🔍
06/22/2017 +0 days 🔍
06/23/2017 +1 days 🔍
06/27/2017 +4 days 🔍
12/29/2020 +1281 days 🔍

Sourcesinfo

Advisory: The OpenVPN post-audit bug bonanza
Researcher: Guido Vranken
Organization: https://guidovranken.wordpress.com
Status: Not defined
Confirmation: 🔍

CVE: CVE-2017-7520 (🔍)
GCVE (CVE): GCVE-0-2017-7520
GCVE (VulDB): GCVE-100-102712

OVAL: 🔍

SecurityFocus: 99230 - OpenVPN Multiple Security Vulnerabilities
SecurityTracker: 1038768

See also: 🔍

Entryinfo

Created: 06/21/2017 17:48
Updated: 12/29/2020 11:23
Changes: 06/21/2017 17:48 (71), 10/19/2019 14:19 (17), 12/29/2020 11:23 (3)
Complete: 🔍
Cache ID: 216::103

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