Microsoft Windows WinVerifyTrust Authenticode Signature Bypass and Remote Code Execution Vulnerability (CVE-2013-3900)
Executive & SecOps Summary
SECOPS ASSESSMENTAll currently supported versions of Microsoft Windows, including Windows 10, Windows 11, and Windows Server
Attackers can inject malicious code into the unverified padding areas of signed PE files without invalidating the digital signature, bypassing security controls to execute arbitrary code
Enable the 'EnableCertPaddingCheck' registry setting to enforce strict Authenticode signature verification across all endpoints
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Microsoft does not plan to enforce this stricter verification behavior by default. Administrators must opt-in by configuring the registry. Run the following PowerShell commands with administrative privileges to enable the protection:
# Enable strict Authenticode padding verification for 64-bit and 32-bit environments
$RegPaths = @(
'HKLM:\Software\Microsoft\Cryptography\Wintrust\Config',
'HKLM:\Software\Wow6432Node\Microsoft\Cryptography\Wintrust\Config'
)
foreach ($Path in $RegPaths) {
if (-not (Test-Path $Path)) {
New-Item -Path $Path -Force | Out-Null
}
New-ItemProperty -Path $Path -Name 'EnableCertPaddingCheck' -Value '1' -PropertyType 'String' -Force | Out-Null
}
Write-Host 'Authenticode padding check has been successfully enabled.' -ForegroundColor Green2. Temporary Workaround & Hardening Configuration
If immediate registry modification is not feasible, implement strict Windows Defender Application Control (WDAC) or AppLocker policies to restrict the execution of unsigned or untrusted binaries, and monitor execution of signed binaries from untrusted paths (e.g., %TEMP%).
3. Log Audit & IoC Verification Commands
Use the following PowerShell script to audit the compliance status of your endpoints regarding the EnableCertPaddingCheck configuration:
# Audit script to verify EnableCertPaddingCheck status
$PathsToCheck = @(
'HKLM:\Software\Microsoft\Cryptography\Wintrust\Config',
'HKLM:\Software\Wow6432Node\Microsoft\Cryptography\Wintrust\Config'
)
foreach ($Path in $PathsToCheck) {
if (Test-Path $Path) {
$Value = Get-ItemPropertyValue -Path $Path -Name 'EnableCertPaddingCheck' -ErrorAction SilentlyContinue
if ($Value -eq '1') {
Write-Host "[SECURE] $Path is configured correctly (Value: $Value)." -ForegroundColor Green
} else {
Write-Host "[VULNERABLE] $Path exists but EnableCertPaddingCheck is NOT set to 1." -ForegroundColor Red
}
} else {
Write-Host "[VULNERABLE] $Path does not exist. Padding check is disabled." -ForegroundColor Red
}
}Block Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
Protect unpatched Windows, Linux, and macOS workloads against in-memory exploitation and lateral movement with autonomous EDR.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability exists in the way the Windows WinVerifyTrust function handles Authenticode signature verification for Portable Executable (PE) files. The root cause is a structural flaw in the Authenticode specification (CWE-347) where certain non-critical sections of a PE file, such as the padding area after the signature table, are not included in the hash calculation. This allows modification of the file content without breaking the cryptographic validity of the digital signature.
2. Exploitation Mechanics & Attack Scenario
An attacker can take a legitimately signed executable file and append a malicious payload to its unverified padding section. When the modified file is evaluated by WinVerifyTrust, the API verifies the signature successfully and reports the file as trusted. When executed, the operating system runs the file without security warnings, allowing the embedded malicious payload to execute with the privileges of the running user.
3. Infrastructure & Business Impact
As a CISA KEV-listed vulnerability, this flaw has been actively exploited in the wild by sophisticated threat actors. Successful exploitation allows attackers to bypass application whitelisting, EDR detection, and antivirus solutions that rely on digital signature verification. This can lead to complete system compromise, unauthorized software installation, data exfiltration, and lateral movement within the enterprise network.
Official Vendor Advisories & References
Why is Microsoft republishing a CVE from 2013? We are republishing CVE-2013-3900 in the Security Update Guide to update the Security Updates table and to inform customers that the EnableCertPaddingCheck is available in all currently supported versions of Windows 10 and Windows 11. While the format is different from the original CVE published in 2013, except for clarifications about how to configure the EnableCertPaddingCheck registry value, the information herein remains unchanged from the original text published on December 10, 2013, Microsoft does not plan to enforce the stricter verification behavior as a default functionality on supported releases of Microsoft Windows. This behavior remains available as an opt-in feature via reg key setting, and is available on supported editions of Windows released since December 10, 2013. This includes all currently supported versions of Windows 10 and Windows 11. The supporting code for this reg key was incorporated at the time of release for Windows 10 and Windows 11, so no security update is required; however, the reg key must be set. See the Security Updates table for the list of affected software. Vulnerability Description A remote code execution vulnerability exists in the way that the WinVerifyTrust function handles Windows Authenticode signature verification for portable executable (PE) files. An anonymous attacker could exploit the vulnerability by modifying an existing signed executable file to leverage unverified portions of the file in such a way as to add malicious code to the file without invalidating the signature. An attacker who successfully exploited this vulnerability could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. If a user is logged on with administrative user rights, an attacker who successfully exploited this vulnerability could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. Exploitation of this vulnerability requires that a user or application run or install a specially crafted, signed PE file. An attacker could modify an... See more at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2013-3900
Frequently Asked SecOps Questions (CVE-2013-3900)
FAQQ1. How critical is CVE-2013-3900 and is it actively exploited in the wild?
CVE-2013-3900 is rated CVSS 5.5 (MEDIUM) with a 30-day EPSS exploitation probability of 44.6%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2013-3900?
Primary impacted vendors include microsoft across windows, windows_10, windows_11, windows_server. Scope summary: All supported editions of Microsoft Windows 10, Windows 11, and Windows Server. The vulnerability is present by default as Microsoft does not enforce strict verification out-of-the-box.
Q3. What temporary mitigations or workarounds exist for CVE-2013-3900 before patching?
[Mitigation] Enable the 'EnableCertPaddingCheck' registry setting to enforce strict Authenticode signature verification across all endpoints Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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