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Actively exploited

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

Sitecore CMS and Experience Platform (XP) contain a deserialization vulnerability in the Sitecore.Security.AntiCSRF module that allows an authenticated attacker to execute arbitrary code by sending a serialized .NET object in the HTTP POST parameter __CSRFTOKEN.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch urgentlyCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 26 Mar 2025.
  • Rated High severity (CVSS 8.8, scored by CISA).
  • It has been in the catalogue for 590 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

Deserialization of Untrusted Data in the anti CSRF module in Sitecore through 9.1 allows an authenticated attacker to execute arbitrary code by sending a serialized .NET object in an HTTP POST parameter.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Sitecore CMS and Experience Platform (XP). Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated high, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 16 Apr 2025 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

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CVE-2025-53690Sitecore Multiple Products Deserialization of Untrusted Data VulnerabilityAdded 4 Sep 2025CVE-2019-9874Sitecore CMS and Experience Platform (XP) Deserialization VulnerabilityAdded 26 Mar 2025CVE-2021-42237 · RansomwareSitecore XP Remote Command Execution VulnerabilityAdded 25 Mar 2022

All 4 exploited Sitecore vulnerabilities

Not Sure If You Are Exposed?

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2019-9875
  3. CVE record: CVE-2019-9875
  4. FIRST EPSS
  5. support.sitecore.com/kb?id=kb_article_view&sysparm_article=KB0038556
  6. dev.sitecore.net/Downloads.aspx
  7. synacktiv.com/blog.html
  8. synacktiv.com/ressources/advisories/Sitecore_CSRF_deserialize_RCE.pdf