How severe is CVE-2021-42237?

CVE-2021-42237 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which products are affected by CVE-2021-42237?

Affected package information for CVE-2021-42237 is not yet fully mapped. Check the official advisory links for details.

How do I patch CVE-2021-42237?

No patch has shipped for CVE-2021-42237 yet — track the sitecore experience platform advisory for a fixed release and apply the workarounds below in the meantime.

How do I detect CVE-2021-42237 across my infrastructure?

Inventory every sitecore experience platform deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for remote code execution at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.

How do I mitigate CVE-2021-42237 if there is no patch (or I can't update yet)?

Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.

How does O3 Security protect against CVE-2021-42237?

O3 detects and blocks CVE-2021-42237 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.

Is CVE-2021-42237 actively exploited in the wild?

Yes. There are 7 known exploit references for CVE-2021-42237, including 7 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-42237?

CVE-2021-42237 has an EPSS (Exploit Prediction Scoring System) score of 97.9%, placing it in the 100th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

Is CVE-2021-42237 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2021-42237 (Sitecore XP Remote Command Execution Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2022-03-25. CISA required all US federal civilian agencies to remediate this vulnerability by 2022-04-15. The required action was: Apply updates per vendor instructions. This CVE has been used in known ransomware campaigns. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2021-42237?

CVE-2021-42237 is classified as Deserialization of Untrusted Data (CWE-502). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

Which products and versions are affected by CVE-2021-42237?

CVE-2021-42237 affects sitecore experience platform (4 versions, e.g. 7.5, 8.0, 8.1…). Check the affected-products list on this page against your deployed version to confirm exposure.

Is there exploit tooling available for CVE-2021-42237?

A Nuclei detection template exists for CVE-2021-42237, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2021-42237 published, and has it been updated?

CVE-2021-42237 was published on November 5, 2021 and was last updated on July 9, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2022-03-25 — agencies required to remediate by 2022-04-15 · Ransomware

CVE-2021-42237

CRITICAL

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.…

Published

Nov 5, 2021

Updated

Jul 9, 2026

Affected

0 pkgs

Patched

None yet

Exploits

7 known

EPSS Exploitation Probability

via FIRST.org ↗

97.9%probability of exploitation in next 30 days

Very High Risk100th percentile-1.31%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Description

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.

Affected Products

1 product · 24 configurations

Application

experience platformsitecore

4 versions

7.58.08.18.2

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.