Microsoft Windows up to Server 2019 Reparse Point access control

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
5.9	$5k-$25k	0.00

A vulnerability, which was classified as problematic, has been found in Microsoft Windows up to Server 2019 (Operating System). This issue affects some unknown functionality of the component Reparse Point Handler. The manipulation with an unknown input leads to a access control vulnerability. Using CWE to declare the problem leads to CWE-284. The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. Impacted is integrity, and availability.

The weakness was published 10/13/2020 as confirmed security guidance (Website). The advisory is shared at portal.msrc.microsoft.com. The identification of this vulnerability is CVE-2020-16877. The exploitation is known to be easy. The attack may be initiated remotely. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 11/18/2020). MITRE ATT&CK project uses the attack technique T1068 for this issue. The advisory points out:

An elevation of privilege vulnerability exists when Microsoft Windows improperly handles reparse points. An attacker who successfully exploited this vulnerability could overwrite or delete a targeted file that would normally require elevated permissions. To exploit this vulnerability, an attacker would first have to log on to the system. An attacker could then run a specially crafted application that could exploit the vulnerability and overwrite or delete files. The security update addresses the vulnerability by correcting how Windows handles reparse points.

It is declared as proof-of-concept.

Applying a patch is able to eliminate this problem. A possible mitigation has been published immediately after the disclosure of the vulnerability.

Productinfo

Type

Operating System

Vendor

Microsoft

Name

Windows

Version

License

commercial

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB CVSS-B Score: 🔍
VulDB CVSS-BT Score: 🔍
VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.5
VulDB Meta Temp Score: 6.1

VulDB Base Score: 5.4
VulDB Temp Score: 4.9
VulDB Vector: 🔍
VulDB Reliability: 🔍

Vendor Base Score (Microsoft): 7.1
Vendor Vector (Microsoft): 🔍

NVD Base Score: 7.1
NVD Vector: 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
unlock	unlock	unlock	unlock	unlock	unlock
unlock	unlock	unlock	unlock	unlock	unlock
unlock	unlock	unlock	unlock	unlock	unlock

VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Access control
CWE: CWE-284 / CWE-266
ATT&CK: T1068

Local: No
Remote: Yes

Availability: 🔍
Status: Proof-of-Concept

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-Day	unlock	unlock	unlock	unlock
Today	unlock	unlock	unlock	unlock

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Patch
Status: 🔍

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

Timelineinfo

08/04/2020 🔍
10/13/2020 +70 days 🔍
10/13/2020 +0 days 🔍
10/14/2020 +0 days 🔍
11/19/2020 +36 days 🔍

Sourcesinfo

Vendor: microsoft.com
Product: microsoft.com

Advisory: portal.msrc.microsoft.com
Status: Confirmed

CVE: CVE-2020-16877 (🔍)
scip Labs: https://www.scip.ch/en/?labs.20161215

Entryinfo

Created: 10/14/2020 11:11
Updated: 11/19/2020 11:10
Changes: 10/14/2020 11:11 (31), 10/14/2020 11:15 (24), 11/18/2020 07:32 (5), 11/19/2020 11:04 (2), 11/19/2020 11:10 (14)
Complete: 🔍