CVE-2020-17087
Microsoft Windows Kernel Privilege Escalation Vulnerability
Description
CVE-2020-17087 is a HIGH vulnerability affecting Microsoft Windows, carrying a CVSS 3.1 score of 7.8. Microsoft Windows kernel contains an unspecified vulnerability that allows for privilege escalation. The NVD describes this issue as: Windows Kernel Local Elevation of Privilege Vulnerability. Affected products include Microsoft Windows 10 1507, Microsoft Windows 10 1607, Microsoft Windows 10 1803, Microsoft Windows 10 1809, Microsoft Windows 10 1903, and 10 more. This CVE is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog with a remediation deadline of 2022-05-03. With an EPSS score of 0.17833 (95.04th percentile), this vulnerability demonstrates significant real-world exploitation activity and should be prioritized for immediate remediation.
KEV Information
CVSS Score
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HOpen in CalculatorCWEs
Affected Products
| Vendor | Product | Version |
|---|---|---|
| microsoft | windows 10 1507 | - |
| microsoft | windows 10 1607 | - |
| microsoft | windows 10 1803 | - |
| microsoft | windows 10 1809 | - |
| microsoft | windows 10 1903 | - |
| microsoft | windows 10 1909 | - |
| microsoft | windows 10 2004 | - |
| microsoft | windows 10 20h2 | - |
| microsoft | windows 7 | - |
| microsoft | windows 8.1 | - |
| microsoft | windows rt 8.1 | - |
| microsoft | windows server 2008 | -; r2 |
| microsoft | windows server 2012 | -; r2 |
| microsoft | windows server 2016 | -; 20h2; 1903; 1909; 2004 |
| microsoft | windows server 2019 | - |
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://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-17087(Patch, Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-17087(US Government Resource)
Weakness Type
CWE-131: Incorrect Calculation of Buffer Size
CVE-2020-17087 is classified under CWE-131 — Incorrect Calculation of Buffer Size. This weakness category identifies a fundamental flaw in how the affected software handles buffer size calculations, where incorrect computation of a buffer size can lead to buffer overflows or underflows, enabling attackers to write data beyond allocated memory boundaries.
In the context of Microsoft Windows, this weakness is particularly dangerous because it can be leveraged by attackers who have low-level access to the local system to achieve elevated privileges and full system compromise. Organizations should understand that this vulnerability class has historically enabled severe security breaches across enterprise environments.
Learn more: CWE-131 — Incorrect Calculation of Buffer Size
Impact Analysis
CVE-2020-17087 carries a CVSS 3.1 score of 7.8 (HIGH) with Unchanged Scope.
Confidentiality (HIGH): Successful exploitation grants the attacker extensive access to sensitive data processed by Microsoft Windows, including system files, credentials, and potentially data from connected systems.
Integrity (HIGH): Attackers can modify critical system files, install backdoors, alter configurations, or deploy malware on affected systems running Microsoft Windows.
Availability (HIGH): Complete disruption of the affected service or system is possible, including denial of service, system crashes, or rendering Microsoft Windows inoperable.
Scope Unchanged: The vulnerability's scope is Unchanged (U), meaning exploitation is contained within the vulnerable component. The impact, while significant, is limited to the Microsoft Windows environment itself.
With an EPSS score of 0.17833 (95.04th percentile), this vulnerability ranks among the most likely to be exploited in real-world attacks, underscoring the urgency of remediation.
Exploit Maturity
CVE-2020-17087 has confirmed active exploitation in the wild and is listed in CISA's Known Exploited Vulnerabilities catalog.
Exploit status: This vulnerability has been actively exploited, as confirmed by its inclusion in the KEV catalog. The EPSS score of 0.17833 (95.04th percentile) places it among the most exploited vulnerabilities tracked.
Ransomware association: As of the latest KEV data, no direct ransomware association has been confirmed for CVE-2020-17087. However, the confirmed exploitation in the wild means threat actors are actively using this vulnerability in attacks.
Attack surface: The local attack vector requires the attacker to have some form of access to the target system. While this limits the remote attack surface, it is commonly exploited in post-compromise scenarios where attackers have gained initial access through other means (phishing, other vulnerabilities) and then use CVE-2020-17087 for privilege escalation.
KEV deadline: CISA required federal agencies to remediate this vulnerability by 2022-05-03. All organizations should treat this deadline as a strong recommendation for their own remediation timelines.
Remediation
- Apply vendor patches immediately. Apply updates per vendor instructions. Consult the vendor advisory at portal.msrc.microsoft.com for specific patch guidance.
- Verify affected product versions in your environment. Identify all instances of Microsoft Windows in your infrastructure. Affected products include Microsoft Windows 10 1507, Microsoft Windows 10 1607, Microsoft Windows 10 1803, Microsoft Windows 10 1809, Microsoft Windows 10 1903, and 10 more. Use asset inventory and vulnerability scanning tools to ensure no instances are missed.
- Implement interim mitigations if patching is delayed. If immediate patching is not feasible, apply network-level controls such as restricting access to the affected component, enabling enhanced logging, and monitoring for indicators of compromise. Limit local user access and enforce principle of least privilege to reduce exploitation risk.
- Scan for signs of prior exploitation. Given the confirmed active exploitation of this vulnerability, review system logs and security monitoring data for evidence of compromise. Look for unexpected privilege escalation events, unauthorized administrative actions, or suspicious process creation.
- Update detection signatures and monitoring rules. Ensure intrusion detection and prevention systems, endpoint detection tools, and SIEM rules are updated to detect exploitation attempts targeting CVE-2020-17087.
- Conduct a post-remediation review. After patching, verify the fix is effective and document the remediation actions taken. Update your vulnerability management records and assess whether any additional hardening measures are warranted.
Technical Details
CVE-2020-17087 is a HIGH-severity vulnerability in Microsoft Windows that requires local access to exploit. The attack complexity is low, meaning no specialized conditions or preparation are required beyond the attack prerequisites. Low-level privileges are required, meaning an attacker needs basic authenticated access to the system. No user interaction is required, allowing the attack to be fully automated.
Technical mechanism: Windows Kernel Local Elevation of Privilege Vulnerability The underlying flaw relates to Incorrect Calculation of Buffer Size, which involves incorrect calculation of buffer sizes, where the software computes an incorrect size for a buffer, leading to potential memory corruption when data exceeding the allocated size is written.
CVSS 3.1 vector analysis: The vector (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) reflects an Attack Vector of LOCAL, Attack Complexity of LOW, Privileges Required of LOW, User Interaction of NONE, Scope UNCHANGED, and impact ratings of HIGH/HIGH/HIGH for Confidentiality/Integrity/Availability respectively. The Unchanged scope means impact is contained within the vulnerable component itself.
Frequently Asked Questions
Is CVE-2020-17087 being actively exploited?
Yes. CVE-2020-17087 is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. The EPSS score of 0.17833 (95.04th percentile) further confirms its high exploitation likelihood. Organizations should treat this as an urgent security matter requiring immediate attention.
What products are affected by CVE-2020-17087?
The affected products include Microsoft Windows 10 1507, Microsoft Windows 10 1607, Microsoft Windows 10 1803, Microsoft Windows 10 1809, Microsoft Windows 10 1903, and 10 more. Organizations running any of these versions should verify their exposure and prioritize remediation. Check vendor advisories for the complete and most current list of affected versions.
How do I fix CVE-2020-17087?
Apply updates per vendor instructions. Ensure all affected instances of Microsoft Windows are identified using vulnerability scanning and asset management tools. If immediate patching is not possible, implement network-level mitigations and enhanced monitoring. After patching, verify the fix and scan for indicators of prior compromise.
How severe is CVE-2020-17087?
CVE-2020-17087 is rated HIGH with a CVSS 3.1 score of 7.8. Its EPSS score of 0.17833 places it in the 95.04th percentile for exploitation likelihood. The vulnerability has confirmed active exploitation in the wild and was required to be remediated by federal agencies by 2022-05-03 per CISA's KEV directive.
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