CVE-2021-34486
Microsoft Windows Event Tracing Privilege Escalation Vulnerability
Description
CVE-2021-34486 is a privilege escalation vulnerability in the Windows Event Tracing component of Microsoft Windows that allows a locally authenticated attacker to elevate privileges to SYSTEM level. The flaw arises from improper handling of objects in memory by the Event Tracing subsystem, enabling an attacker who has already gained initial code execution on a system to escalate their access rights. CISA added CVE-2021-34486 to the Known Exploited Vulnerabilities catalog on March 28, 2022, confirming real-world exploitation. With an EPSS score of 0.128% (50.6th percentile), the vulnerability represents a moderate but confirmed exploitation risk that should be addressed through regular Windows patching cycles.
KEV Information
CVSS Score
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| microsoft | windows 10 1809 | < 10.0.17763.2114 |
| microsoft | windows 10 1909 | < 10.0.18363.1734 |
| microsoft | windows 10 2004 | < 10.0.19041.1165 |
| microsoft | windows 10 20h2 | < 10.0.19042.1165 |
| microsoft | windows 10 21h1 | < 10.0.19043.1165 |
| microsoft | windows server 2004 | < 10.0.19041.1165 |
| microsoft | windows server 2019 | < 10.0.17763.2114 |
| microsoft | windows server 20h2 | < 10.0.19042.1165 |
Multiple CVSS Assessments
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34486(Patch, Vendor Advisory)
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34486(Patch, Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34486(US Government Resource)
Weakness Type
CWE-269: Improper Privilege Management
CWE-269 describes a weakness where software does not properly manage privileges, allowing attackers to gain elevated access beyond their intended authorization level. In CVE-2021-34486, the Windows Event Tracing component fails to correctly manage privilege boundaries, enabling a local attacker to escalate from a low-privileged user context to SYSTEM-level access.
Learn more: CWE-269 — Improper Privilege Management
Impact Analysis
CVE-2021-34486 enables local privilege escalation to SYSTEM level on affected Windows systems, giving an attacker complete control over the compromised host. While the vulnerability requires the attacker to already have local code execution, successful exploitation grants full access to all system resources, files, and credentials stored on the machine. The impact on confidentiality and integrity is high, as SYSTEM-level access allows reading and modifying any data on the system, including security logs and credential stores. Organizations running unpatched Windows systems should treat this as a significant post-compromise risk that can dramatically amplify the damage of an initial breach.
Exploit Maturity
CVE-2021-34486 has been confirmed as actively exploited in the wild by CISA, which added it to the KEV catalog on March 28, 2022. The EPSS score of 0.128% (50.6th percentile) reflects moderate exploitation probability, consistent with a local privilege escalation vulnerability that requires prior system access. While no public proof-of-concept exploits are widely circulated, the KEV listing confirms that threat actors have incorporated this vulnerability into post-compromise attack chains.
Remediation
- Apply the Microsoft security update from August 2021 (Patch Tuesday) that addresses CVE-2021-34486 across all affected Windows versions.
- Ensure Windows Update is enabled and configured for automatic security updates to prevent future delays in patching known exploited vulnerabilities.
- Implement the principle of least privilege across all endpoints to limit the impact of local privilege escalation vulnerabilities, restricting standard user accounts from running unnecessary administrative tools.
- Deploy endpoint detection and response (EDR) solutions capable of detecting anomalous Event Tracing activity and privilege escalation attempts on Windows systems.
Technical Details
CVE-2021-34486 is a local privilege escalation vulnerability in the Windows Event Tracing subsystem caused by improper handling of objects in memory. When the Event Tracing component processes certain operations, it fails to properly validate or manage memory objects, creating a condition that a local attacker can exploit to execute code with elevated SYSTEM privileges. The attack vector is local (AV:L), requiring the attacker to have already established code execution on the target system, but the attack complexity is low and no user interaction is required. The vulnerability affects multiple versions of Windows 10 and Windows Server, and successful exploitation results in complete system compromise from an initially low-privileged context.
Frequently Asked Questions
Is CVE-2021-34486 being actively exploited?
Yes, CVE-2021-34486 is confirmed as actively exploited in the wild. CISA added it to the Known Exploited Vulnerabilities catalog on March 28, 2022, indicating confirmed real-world exploitation by threat actors as part of post-compromise attack chains on Windows systems.
What systems are affected by CVE-2021-34486?
CVE-2021-34486 affects multiple versions of Microsoft Windows, including Windows 10 and Windows Server editions that include the vulnerable Event Tracing component. All unpatched systems running affected Windows versions are susceptible to local privilege escalation.
How do I fix CVE-2021-34486?
Apply the Microsoft security update from the August 2021 Patch Tuesday release that addresses CVE-2021-34486. Ensure Windows Update is enabled for automatic security updates. Additionally, implement least privilege policies to limit the blast radius of privilege escalation attacks.
How severe is CVE-2021-34486?
CVE-2021-34486 is a local privilege escalation vulnerability that enables SYSTEM-level access on Windows systems. While it requires prior local access (limiting initial attack surface), it is confirmed exploited in the wild and poses a significant risk as part of multi-stage attacks where an attacker chains initial access with privilege escalation to achieve full system compromise.
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