Insights and Research

Microsoft vulnerability: Source code published for three zero-day vulnerabilities in Windows


A security researcher (with the pseudonym SandboxEscaper) has discovered three zero-day vulnerabilities in Microsoft Windows. Their POC and source code have been released on GitHub. Two of these are local privilege escalation (LPE) vulnerabilities. They have been tested to work on Windows 10 only. The third vulnerability is a sandbox bypass vulnerability in Internet Explorer 11 (IE11). As of this writing, no patch has been released by Microsoft for these vulnerabilities.

What is the issue?

The security researcher has published three POCs: angrypolarbearbug2, bearlpe, and sandboxescape. 

The first vulnerability – angrypolarbearbug2 – can be exploited by performing specially crafted DACL (discretionary access control list) operations when the Windows Error Reporting service tries to write a DACL for the given Windows Error Reporting (.wer) file. Once successfully exploited, the vulnerability gives SYSTEM privileges to the attacker.

The second vulnerability – bearlpe – targets the way the Windows task scheduler service uses the SetJobFileSecurityByName() function to write DACL for the job file. For this exploit to work, one needs to have "schtasks.exe" and "schedsvc.dll" files from Windows XP. Once successfully exploited, the vulnerability gives SYSTEM privileges to the attacker.

The third vulnerability – sandboxescape – bypasses the IE11 sandbox and allows an attacker to execute code in IE low protection mode. To exploit this vulnerability, an attacker needs to inject a special DLL in the IE process. According to reports, this exploit cannot be triggered remotely.

What systems are impacted?

The POC has been tested on Windows 10 32-bit and 64-bit and IE11.

Zscaler coverage

Advanced Threat Signatures:
Win32. Exploit.CVE.2019.0863

Zscaler Cloud Sandbox provides proactive coverage against exploit payloads and advanced threats like ransomware, and the Zscaler ThreatLabZ team is actively monitoring for in-the-wild exploit attempts to ensure coverage.

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