Known exploited · Sitecore
CVE-2019-9874: Sitecore CMS and Experience Platform (XP) Deserialization Vulnerability
What it is
Sitecore CMS and Experience Platform (XP) contain a deserialization vulnerability in the Sitecore.Security.AntiCSRF module that allows an unauthenticated attacker to execute arbitrary code by sending a serialized .NET object in the HTTP POST parameter __CSRFTOKEN.
- Vendor
- Sitecore
- Product
- CMS and Experience Platform (XP)
- Added to KEV
- March 26, 2025
- CISA due date
- April 16, 2025
- Ransomware use
- Unknown
What CISA requires
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Forensic triage
No
What to do now
- Find every instance of CMS and Experience Platform (XP) you run, including the forgotten ones, and check its version against the vendor advisory.
- Apply the vendor's fix or mitigation, before April 16, 2025 if you are bound by CISA's deadline, sooner if it faces the internet.
- Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
- Until every instance is patched, block the attack at the edge: a WAF in blocking mode stops Java deserialization payloads.
References
The Dome
Block it at the edge while you patch
The Dome's WAF runs the OWASP Core Rule Set in blocking mode and stops Java deserialization payloads before they reach your application.
See the DomeT Academy
Train the engineers who fix it
Security engineering on real hosts in the browser, every objective checked on the machine. The first two lessons of Linux 1 are free.
Start freeSource: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.