Skip to main content
Live Webinar with SANS (June 25)— Agentic CTI Automation for Fun & ProfitRegister Free
Mallory
MediumCISA KEVExploited in the wildPublic exploit

Windows Installer Elevation of Privilege Vulnerability

IdentifiersCVE-2021-41379CWE-269

CVE-2021-41379 is a local privilege escalation vulnerability in Microsoft Windows Installer. The provided content identifies it as a Windows Installer elevation of privilege issue and indicates it has been abused via DLL side-loading behavior involving msi.dll. The content further states that analysis of the patch for CVE-2021-41379 led researchers to identify a related locally exploitable Windows issue affecting systems with the AppX Installer/Elevation service enabled, and that a reliable proof-of-concept was published. Based on the supplied material, exploitation involves local abuse of Windows installer-related components to execute arbitrary code with elevated privileges, but the specific vulnerable function or code path is not provided in the source content.

Share:
For your environment

Are you exposed to this one?

Mallory correlates every CVE against your assets, your vendors, and active adversary campaigns. Know which vulnerabilities matter for you, not just which ones are loud.

ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows a local attacker to elevate privileges and execute arbitrary code with elevated rights. The supporting content also notes that confirmed abuse may enable persistence and unauthorized system modification. In intrusion chains such as those described for Makop ransomware activity, this type of privilege escalation can be used to disable defenses, dump credentials, move laterally, and ultimately deploy ransomware with higher privileges.

Mitigation

If you can’t patch tonight, do this now.

Restrict local code execution opportunities for untrusted users, reduce exposure of initial access vectors such as insecure RDP, and monitor for suspicious loading of msi.dll by binaries outside standard Windows directories. The supplied content specifically highlights Sysmon Event ID 7-based detection for nonstandard msi.dll loads as a useful hunting analytic. Additional mitigations include application control, least-privilege enforcement, and hardening or disabling unnecessary installer/elevation-related services where operationally feasible.

Remediation

Patch, then assume compromise.

Apply Microsoft's security update for CVE-2021-41379 on affected Windows systems. Because the supplied content also references a related bypass or variant discovered through patch analysis and states that, at that time, no corrective update was yet available for the newly identified issue, defenders should ensure they are using the latest cumulative Windows updates and monitor Microsoft guidance for any superseding fixes addressing installer/elevation-service abuse.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
Microsoft CorporationWindows 10 1507operating_system
Microsoft CorporationWindows 10 1607operating_system
Microsoft CorporationWindows 10 1809operating_system
Microsoft CorporationWindows 10 1909operating_system
Microsoft CorporationWindows 10 2004operating_system
Microsoft CorporationWindows 10 20h2operating_system
Microsoft CorporationWindows 10 21h1operating_system
Microsoft CorporationWindows 11 21h2operating_system
Microsoft CorporationWindows 7operating_system
Microsoft CorporationWindows 8.1operating_system
Microsoft CorporationWindows Rt 8.1operating_system
Microsoft CorporationWindows Server 2004operating_system
Microsoft CorporationWindows Server 2008operating_system
Microsoft CorporationWindows Server 2008 R2operating_system
Microsoft CorporationWindows Server 2008 Sp2operating_system
Microsoft CorporationWindows Server 2012operating_system
Microsoft CorporationWindows Server 2012 R2operating_system
Microsoft CorporationWindows Server 2016operating_system
Microsoft CorporationWindows Server 2019operating_system
Microsoft CorporationWindows Server 2022operating_system
Microsoft CorporationWindows Server 20h2operating_system

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.
Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware1

Malware families riding this exploit, with evidence and IOCs.

Detection signatures1

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity

Community discussion across Reddit, Mastodon, and other social sources.