Sitecore CMS and XP AntiCSRF Module Deserialization Remote Code Execution (RCE) (CVE-2019-9874)
Executive & SecOps Summary
SECOPS ASSESSMENTSitecore CMS 7.0 to 7.2 and Sitecore XP 7.5 to 8.2
Unauthenticated remote attackers can execute arbitrary code with system privileges by sending a malicious serialized .NET object in the __CSRFTOKEN HTTP POST parameter
Apply official security patches, disable the vulnerable AntiCSRF module, or upgrade to a supported secure version
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Upgrade to the latest supported secure version of Sitecore or apply the official hotfix provided by the vendor.
# Example: Update the Sitecore.Security.AntiCSRF package via NuGet Package Manager Console
Update-Package Sitecore.Security.AntiCSRF -Version [Secure_Patch_Version]2. Temporary Workaround & Hardening Configuration
If patching cannot be applied immediately, disable the vulnerable AntiCSRF module in the web.config file to mitigate the risk.
<!-- Locate and comment out or remove the AntiCSRF module in web.config -->
<configuration>
<system.webServer>
<modules>
<!-- Comment out the vulnerable module to mitigate the threat immediately -->
<!-- <add name='SitecoreAntiCSRF' type='Sitecore.Security.AntiCSRF.AntiCSRFModule, Sitecore.Security.AntiCSRF' /> -->
</modules>
</system.webServer>
</configuration>3. Log Audit & IoC Verification Commands
Monitor IIS logs for anomalous POST requests containing large or suspicious __CSRFTOKEN values, and audit process creation events.
# PowerShell command to search IIS logs for suspicious __CSRFTOKEN patterns
Select-String -Path 'C:\inetpub\logs\LogFiles\W3SVC1\*.log' -Pattern '__CSRFTOKEN'
# Detect anomalous child processes spawned by the IIS worker process (w3wp.exe)
Get-WmiObject Win32_Process -Filter "Name='cmd.exe' or Name='powershell.exe'" | Where-Object {
(Get-Process -Id $_.ParentProcessId).ProcessName -eq 'w3wp'
}Block Exploits Instantly with Managed Virtual Patching Rules
Can't patch production immediately? Deploy managed WAF rules at the edge to intercept RCE, SQLi, and deserialization payloads before they hit your origin server.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability exists in the Sitecore.Security.AntiCSRF module of Sitecore CMS and XP due to the unsafe deserialization of untrusted data. When validating CSRF tokens, the module processes the __CSRFTOKEN parameter from HTTP POST requests without proper validation. By utilizing unsafe .NET deserialization formatters (such as BinaryFormatter), the application instantiates arbitrary object graphs provided by the attacker, leading to remote code execution.
2. Exploitation Mechanics & Attack Scenario
An unauthenticated attacker can exploit this vulnerability remotely. The attack flow typically proceeds as follows:
- The attacker generates a malicious .NET deserialization payload using gadget chains (e.g., via
ysoserial.netusingActivitySurrogateSelectororTypeConfuseDelegate). - The payload is encoded (Base64 or Hex) and embedded into the
__CSRFTOKENparameter of an HTTP POST request. - Upon receiving the request, the Sitecore AntiCSRF module attempts to deserialize the token, triggering the gadget chain and executing arbitrary OS commands under the security context of the IIS worker process (w3wp.exe).
3. Infrastructure & Business Impact
With a CVSS score of 9.8 (Critical) and its inclusion in the CISA KEV catalog, this vulnerability poses an immediate threat to enterprise infrastructure. Successful exploitation grants full control over the web server, enabling attackers to perform lateral movement, exfiltrate sensitive databases, deploy ransomware, or compromise internal networks.
Official Vendor Advisories & References
Deserialization of Untrusted Data in the Sitecore.Security.AntiCSRF (aka anti CSRF) module in Sitecore CMS 7.0 to 7.2 and Sitecore XP 7.5 to 8.2 allows an unauthenticated attacker to execute arbitrary code by sending a serialized .NET object in the HTTP POST parameter __CSRFTOKEN.
Frequently Asked SecOps Questions (CVE-2019-9874)
FAQQ1. How critical is CVE-2019-9874 and is it actively exploited in the wild?
CVE-2019-9874 is rated CVSS 9.8 (CRITICAL) with a 30-day EPSS exploitation probability of 83.7%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2019-9874?
Primary impacted vendors include sitecore across sitecore_cms, sitecore_xp. Scope summary: Sitecore CMS versions 7.0 to 7.2 and Sitecore XP versions 7.5 to 8.2 with the Sitecore.Security.AntiCSRF module enabled
Q3. What temporary mitigations or workarounds exist for CVE-2019-9874 before patching?
[Mitigation] Apply official security patches, disable the vulnerable AntiCSRF module, or upgrade to a supported secure version Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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