Sitecore CMS and XP Deserialization Vulnerability (CVE-2019-9875)

Historical catalog analysis: CISA added this entry on March 26, 2025. The entry reflects catalog information retrieved on August 31, 2026, not a snapshot archived on the inclusion date. Check current vendor guidance before acting.

What the vulnerability is

CVE-2019-9875 is a deserialization vulnerability (CWE-502) located within the Sitecore.Security.AntiCSRF module of Sitecore CMS and Experience Platform (XP). The flaw allows an authenticated attacker to execute arbitrary code on the underlying system by submitting a serialized .NET object through the __CSRFTOKEN HTTP POST parameter.

Exposure and applicability

This vulnerability applies to environments running affected versions of Sitecore CMS and Experience Platform (XP) where the AntiCSRF module is active. Because the attack vector requires authentication, exposure is highest in environments with broad authenticated access or those where compromised credentials could be leveraged to move laterally into the CMS infrastructure.

Remediation priorities

Based on the reported vulnerability, our analysis suggests the following prioritization for vulnerability management teams:

1. Asset Identification: Identify all instances of Sitecore CMS and XP across the environment, specifically verifying if the Sitecore.Security.AntiCSRF module is in use.
2. Vendor Mitigation: Prioritize the application of mitigations as specified by the vendor’s instructions to address the deserialization path.
3. Cloud Service Review: For organizations utilizing these products via cloud services, review and apply guidance consistent with BOD 22-01 to ensure provider-side mitigations are active.
4. Decommissioning: In cases where vendor mitigations cannot be applied or are unavailable for a specific legacy version, the product should be discontinued to eliminate the exposure.

How to validate remediation

Verification must move beyond simple version checks, as a deployed patch does not always guarantee that the configuration is secure. To verify that the risk has been reduced, defenders should:

• Configuration Audit: Confirm that the specific module (Sitecore.Security.AntiCSRF) has been updated or replaced according to vendor specifications.
• Input Validation Testing: In a controlled staging environment, attempt to send non-standard serialized objects via the __CSRFTOKEN parameter to ensure the system no longer processes them as executable code.
• Log Analysis: Monitor for unexpected errors or blocked requests associated with the __CSRFTOKEN parameter that may indicate the mitigation is actively rejecting malformed inputs.

Limits and open questions

While the vulnerability requires authentication, the source does not specify the minimum privilege level required to trigger the flaw. It remains unknown whether a low-privileged user can execute this attack or if administrative rights are necessary. Additionally, while mitigations reduce the likelihood of exploitation, residual risk may remain if other deserialization vectors exist within the platform that are not addressed by this specific fix.

Source and editorial note

CVE-2019-9875: Sitecore CMS and Experience Platform (XP) Deserialization Vulnerability · Source date: March 26, 2025 · Retrieved August 31, 2026.

Material facts are tied to the cited primary source. Recommendations are independent defensive analysis unless attributed to the source. Confirm consequential decisions against current authoritative guidance.

Archive date: March 29, 2025. The displayed post date is assigned three days after the source date to organize this retrospective archive; it does not mean this site published the analysis then. First published by this site: October 20, 2026 at 00:27 UTC.

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