CVE-2024-30020: Windows 10 1507 RCE Vulnerability

CVE-2024-30020 Overview

CVE-2024-30020 is a remote code execution vulnerability in Windows Cryptographic Services. The flaw affects supported Windows client and server releases, including Windows 10, Windows 11, and Windows Server 2008 through Windows Server 2022 23H2. Microsoft addressed the issue in the May 2024 Patch Tuesday release.

The vulnerability combines a heap-based buffer overflow [CWE-122] with improper certificate validation [CWE-295] in the cryptographic subsystem. An unauthenticated network attacker who wins a race or coerces a victim into processing a crafted certificate can achieve code execution. The EPSS score of 4.31% places this CVE in the 89th percentile for exploit likelihood.

Critical Impact

Successful exploitation leads to remote code execution in the context of Windows Cryptographic Services, impacting confidentiality, integrity, and availability across all supported Windows versions.

Affected Products

• Microsoft Windows 10 (versions 1507, 1607, 1809, 21H2, 22H2)
• Microsoft Windows 11 (versions 21H2, 22H2, 23H2)
• Microsoft Windows Server 2008, 2012, 2012 R2, 2016, 2019, 2022, and 2022 23H2

Discovery Timeline

• 2024-05-14 - Microsoft releases security patch as part of Patch Tuesday
• 2024-05-14 - CVE-2024-30020 published to NVD
• 2025-08-27 - Last updated in NVD database

Technical Details for CVE-2024-30020

Vulnerability Analysis

The vulnerability resides in Windows Cryptographic Services, the core subsystem responsible for certificate validation, signature verification, and cryptographic operations. According to Microsoft's advisory, the flaw enables remote code execution when the service processes attacker-controlled certificate data. The two weaknesses tracked alongside this CVE are a heap-based buffer overflow [CWE-122] and improper certificate validation [CWE-295].

An attacker exploits the issue by inducing the target system to parse a malformed X.509 certificate. Improper validation logic accepts the crafted certificate, and downstream parsing triggers a heap corruption condition. The attacker controls memory adjacent to the corrupted allocation and can pivot to arbitrary code execution.

Exploitation requires no privileges and no user interaction, but the attack complexity is high. The high complexity rating reflects the need to win a timing condition or stage specific preconditions during certificate processing.

Root Cause

The root cause is a heap-based buffer overflow reachable through the certificate validation path in Windows Cryptographic Services. Insufficient bounds checking during the processing of certificate fields allows attacker-supplied data to overwrite adjacent heap memory. The companion certificate validation weakness permits the malformed input to reach the vulnerable parsing routine in the first place.

Attack Vector

The attack vector is network-based. An attacker delivers a crafted certificate through any channel where Windows Cryptographic Services performs validation. Relevant channels include TLS handshakes, S/MIME message processing, code-signing verification, and authenticated network protocols that rely on certificate chains. Successful exploitation yields code execution in the security context of the cryptographic service.

No verified public proof-of-concept code is available. The vulnerability is described in prose because no exploit samples or patch diffs have been published by Microsoft or third parties. Refer to the Microsoft Security Update CVE-2024-30020 advisory for vendor guidance.

Detection Methods for CVE-2024-30020

Indicators of Compromise

• Unexpected crashes or restarts of the CryptSvc service or processes that consume crypt32.dll
• Anomalous outbound TLS connections that present malformed or oversized certificate fields
• New or unsigned binaries written to disk shortly after certificate validation events
• Event Log entries showing certificate chain failures followed by process anomalies

Detection Strategies

• Monitor Windows Event Log channels Microsoft-Windows-CАPI2/Operational and System for repeated certificate validation errors paired with service crashes
• Inspect network telemetry for X.509 certificates with abnormally large field lengths or non-conformant ASN.1 encoding
• Hunt for child processes of svchost.exe hosting CryptSvc that spawn shells, scripting engines, or LOLBins
• Correlate certificate parsing errors with subsequent process creation events on the same host

Monitoring Recommendations

• Track patch deployment status across all Windows endpoints and servers via configuration management telemetry
• Enable command-line and module-load auditing to capture activity following certificate processing
• Forward Sysmon Event IDs 1, 7, and 11 to a centralized analytics platform for correlation
• Baseline normal certificate validation volumes and alert on sudden spikes from a single source

How to Mitigate CVE-2024-30020

Immediate Actions Required

• Apply the May 2024 Microsoft security updates to all affected Windows clients and servers without delay
• Prioritize internet-facing systems and servers that terminate TLS or process external certificates
• Verify patch installation by confirming the relevant KB article is present in wmic qfe list output
• Restrict inbound connections to systems pending patch deployment using host or network firewalls

Patch Information

Microsoft released fixes for CVE-2024-30020 on May 14, 2024. Refer to the Microsoft Security Update Guide for the specific KB articles that apply to each Windows version. Install the cumulative update appropriate for the operating system release and verify the build number after reboot.

Workarounds

• No vendor-supplied workaround exists; patching is the only complete remediation
• Reduce exposure by terminating untrusted TLS connections at an inspection proxy that enforces strict certificate parsing
• Disable or restrict services that accept external certificates from untrusted sources where business requirements permit
• Apply network segmentation to limit which systems can deliver certificates to Windows hosts running cryptographic services

# Verify the May 2024 cumulative update is installed
wmic qfe list brief /format:table | findstr /i "KB5037"

# PowerShell alternative
Get-HotFix | Where-Object { $_.InstalledOn -ge [datetime]'2024-05-14' } | Sort-Object InstalledOn