Zero-day vulnerability in Windows

Privilege escalation
CVE-2018-8440

A privilege escalation vulnerability was first publicly disclosed on Twitter on August 27, 2018. It was successful incorporated into malware used by the PowerPool group, reported by ESET.
The vulnerability was dubbed SendboxEscaper by its author.

Vulnerability details

Advisory: SB2018082901 - Privilege escalation in Microsoft Windows

Vulnerable component: Windows

CVE-ID: CVE-2018-8440

CVSSv3 score: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:H/RL:O/RC:C

CWE-ID: CWE-264 - Permissions, Privileges, and Access Controls

Description:

The vulnerability allows a local attacker to gain elevated privileges on the target system.

The vulnerability exists due to ALPC access control flaw. A local attacker can create a hard link from a readable file on the system to a '.job' file in the 'c:\windows\tasks' directory, invoke the _SchRpcSetSecurity() method of the task scheduler service ALPC endpoint to overwrite the linked file and gain system level privileges on the target system. The vulnerability was dubbed "SendboxEscaper".

Note: the vulnerability is being exploited in the wild by the PowerPool group.

External links:

https://www.welivesecurity.com/2018/09/05/powerpool-malware-exploits-zero-day-vulnerability/

About zero-day vulnerabilities

Zero-day vulnerability is an undisclosed vulnerability in software that hackers can exploit to compromise computer programs, gain unauthorized access to sensitive data, penetrate networks, etc. We consider vulnerability a zero-day when there is no solution provided from software vendor and the vulnerability is being actively exploited by malicious actors.

Zero-day candidate is a potential zero-day vulnerability in software which might have been used in targeted attacks, however there is no evidence to support this suggestion.