What is CVE-2021-42237?

CVE-2021-42237 is a critical-severity vulnerability in Sitecore Experience Platform, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2021-11-05.

How severe is CVE-2021-42237?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2021-42237 known to be exploited?

Yes. CVE-2021-42237 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-03-25), indicating it is being actively exploited. 21 public proof-of-concept repositories are indexed.

Deserialization in Sitecore Experience Platform

CVE-2021-42237

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.

Vulnerability class: Insecure Deserialization

Published 2021-11-05 · last modified 2026-07-09.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.976 (99.9th percentile), scored 2026-10-15.

Very high probability of exploitation in the next 30 days — among the top 0.1% most-likely-to-be-exploited CVEs. 100th percentile — 99.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.979 · newest: 0.976 · change: -0.003

Affected products

Sitecore Experience Platform — versions 7.5, 8.0, 8.1

Weakness classification (CWE)

CWE-502 — Deserialization of Untrusted Data

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2022-03-25. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2022-04-15.

Required action: Apply updates per vendor instructions.

Known ransomware campaign use: yes.

Public proof-of-concept exploits

References

af854a3a-2127-422b-91ae-364da2661108 (Vendor Advisory)
support.sitecore.com/kb (Vendor Advisory)
blog.assetnote.io/2021/11/02/sitecore-rce/ (Exploit, Third Party Advisory)
packetstormsecurity.com/files/164988/Sitecore-Experience-Platform-XP-Remote-Cod… (VDB Entry, Third Party Advisory)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)

Frequently asked questions

What is CVE-2021-42237?: CVE-2021-42237 is a critical-severity vulnerability in Sitecore Experience Platform, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2021-11-05.
How severe is CVE-2021-42237?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2021-42237 known to be exploited?: Yes. CVE-2021-42237 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-03-25), indicating it is being actively exploited. 21 public proof-of-concept repositories are indexed.