+44 1865 950 828 Secure Your Business
Actively exploitedKnown ransomware use

CVE-2021-42237 Sitecore XP Remote Command Execution Vulnerability

Sitcore XP contains an insecure deserialization vulnerability which can allow for remote code execution.

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

Our Assessment

Should You Worry?

Patch nowCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 25 Mar 2022.
  • CISA lists it as known to be used in ransomware campaigns.
  • Rated Critical severity (CVSS 9.8, scored by CISA).
  • It has been in the catalogue for 1,687 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

Sitecore XP 7.5 Initial Release to Sitecore XP 8.2 Update-7 is vulnerable to an insecure deserialization attack where it is possible to achieve remote command execution on the machine. No authentication or special configuration is required to exploit this vulnerability.

From Watch to Action

What To Do Now

  1. 1

    Find it

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

    Attack Surface Management
  2. 2

    Fix it

    Apply updates per vendor instructions.

    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 critical, 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 15 Apr 2022 to remediate. A sensible benchmark for everyone else.

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

Stay Ahead

More Exploited Sitecore Flaws

Get alerts for SitecoreWe email you when a new Sitecore vulnerability is confirmed as exploited. Add more vendors on Threat Watch.

By signing up you agree to receive Threat Watch alerts. Unsubscribe at any time. See our Privacy Policy.

CVE-2025-53690Sitecore Multiple Products Deserialization of Untrusted Data VulnerabilityAdded 4 Sep 2025CVE-2019-9875Sitecore CMS and Experience Platform (XP) Deserialization VulnerabilityAdded 26 Mar 2025CVE-2019-9874Sitecore CMS and Experience Platform (XP) Deserialization VulnerabilityAdded 26 Mar 2025

All 4 exploited Sitecore vulnerabilities

Not Sure If You Are Exposed?

Our attack surface and vulnerability teams can check your internet-facing estate for CVE-2021-42237 and every other exploited flaw on the list.

Check My Exposure
Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2021-42237
  3. CVE record: CVE-2021-42237
  4. FIRST EPSS
  5. support.sitecore.com/kb?id=kb_article_view&sysparm_article=KB1000776
  6. blog.assetnote.io/2021/11/02/sitecore-rce/
  7. packetstormsecurity.com/files/164988/Sitecore-Experience-Platform-XP-Remote-Code-Execution.html