CVE-2021-41379

Improper Link Resolution in Windows Installer Elevation of Privilege Vulnerability

Verified by Precogs Threat Research
Last Updated: Oct 30, 2025
Base Score
5.5MEDIUM

Executive Summary

CVE-2021-41379 is a medium severity vulnerability affecting appsec. It is classified as CWE-59. This vulnerability is actively being exploited in the wild.

Precogs AI Insight

"The Windows Installer improperly handles filesystem junctions during specific update repair operations, bypassing intended directory restrictions. A local attacker can create a malicious junction to trick the installer into overwriting critical system files, thereby escalating their privileges to SYSTEM. Precogs AI Analysis Engine identifies unsafe file operation handlers and improper logical link resolution."

Exploit Probability (EPSS)
Low (1.2%)
Public POC
Available
Exploit Probability
Low (<10%)
Public POC
Actively Exploited
Affected Assets
appsecCWE-59

What is this vulnerability?

CVE-2021-41379 is categorized as a medium Improper Link Resolution flaw with a CVSS base score of 5.5. Based on our vulnerability intelligence, this issue occurs when the application fails to securely handle untrusted data boundaries.

Windows Installer Elevation of Privilege Vulnerability

This architectural defect enables adversaries to bypass intended security controls, directly manipulating the application's execution state or data layer. Immediate strategic intervention is required.

Risk Assessment

MetricValue
CVSS Base Score5.5 (MEDIUM)
Vector StringCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
PublishedNovember 10, 2021
Last ModifiedOctober 30, 2025
Related CWEsCWE-59, CWE-59

Impact on Systems

Data Exfiltration: Attackers can extract sensitive data from backend databases, configuration files, or internal services.

Authentication Bypass: Exploiting this flaw may allow unauthorized access to protected resources and administrative interfaces.

Lateral Movement: Once initial access is gained, attackers can pivot to internal systems and escalate privileges.

How to Fix and Mitigate CVE-2021-41379

  1. Apply Vendor Patches Immediately: This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog. Apply updates per vendor instructions.
  2. Verify Patch Deployment: Confirm all instances are updated using Precogs continuous monitoring.
  3. Review Audit Logs: Investigate historical access logs for indicators of compromise related to this attack surface.
  4. Implement Defense-in-Depth: Deploy WAF rules, network segmentation, and endpoint detection to limit blast radius.

Defending with Precogs AI

Precogs AI Analysis Engine identifies this vulnerability class through semantic code analysis powered by Code Property Graph (CPG) technology, performing inter-procedural taint tracking to detect injection flaws, broken authentication, and insecure data flows across your entire codebase.

Use Precogs to continuously scan your codebase, binaries, APIs, and infrastructure for this vulnerability class and related attack patterns. Our AI-powered detection engine combines static analysis with threat intelligence to identify exploitable weaknesses before attackers do.

Start scanning with Precogs →

Vulnerability Code Signature

Attack Data Flow

StageDetail
SourceUntrusted User Input
VectorInput flows through the application logic without sanitization
SinkExecution or Rendering Sink
ImpactApplication compromise, Logic Bypass, Data Exfiltration

Vulnerable Code Pattern

# ❌ VULNERABLE: Unsanitized Input Flow
def process_request(request):
    user_input = request.GET.get('data')
    # Taint sink: processing untrusted data
    execute_logic(user_input)
    return {"status": "success"}

Secure Code Pattern

# ✅ SECURE: Input Validation & Sanitization
def process_request(request):
    user_input = request.GET.get('data')
    
    # Sanitized boundary check
    if not is_valid_format(user_input):
        raise ValueError("Invalid input format")
        
    sanitized_data = sanitize(user_input)
    execute_logic(sanitized_data)
    return {"status": "success"}

How Precogs Detects This

Precogs AI Analysis Engine maps untrusted input directly to execution sinks to catch complex application security vulnerabilities.\n

Related Vulnerabilitiesvia CWE-59

Is your system affected?

Precogs AI detects CVE-2021-41379 in compiled binaries, LLMs, and application layers — even without source code access.