CVE-2021-42237
CVE-2021-42237 is a security flaw in Sitecore XP. Attackers can run their own code on Sitecore XP from anywhere, without logging in. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 25 Mar 2022, and says ransomware gangs have used it.[1]
Sitecore XP is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Sitecore has published a fix or advice.
Description
CISA calls it a remote command execution in Sitecore XP. In its words: “Sitcore XP contains an insecure deserialization vulnerability which can allow for remote code execution.”[1]
The CVE record adds: “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.”[2]
The underlying weakness is deserialization of untrusted data (CWE-502), in MITRE’s list of common software weaknesses.
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Sitecore’s advisory has them[3]. CISA names the product as Sitecore XP.
Most families won’t have Sitecore XP; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 25 Mar 2022, 140 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 15 Apr 2022 to fix it.[1] CISA says ransomware gangs have used it.
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 98%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Sitecore has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Check whether you use it.Sitecore XP is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 15 Apr 2022 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 9.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks, noting that ransomware gangs have used it.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 98%.[4] |
See also
Other Sitecore flaws
- CVE-2025-53690, Sitecore products: deserialization of untrusted data ·
- CVE-2019-9875, Sitecore CMS and Experience Platform (XP): deserialization ·
- CVE-2019-9874, Sitecore CMS and Experience Platform (XP): deserialization ·
Other deserialization of untrusted data flaws
- CVE-2021-23758, Ajax.NET Professional: deserialization of untrusted data ·
- CVE-2026-63077, JetBrains TeamCity: deserialization of untrusted data ·
- CVE-2026-50522, Microsoft SharePoint: deserialization of untrusted data ·
- CVE-2026-58644, Microsoft SharePoint: deserialization of untrusted data ·
- CVE-2026-45659, Microsoft SharePoint Server: deserialization of untrusted data ·
Added the same day
- CVE-2022-26318, WatchGuard Firebox and XTM Appliances: arbitrary code execution ·
- CVE-2022-26143, Mitel MiCollab, MiVoice Business Express: access control ·
- CVE-2022-21999, Microsoft Windows: print spooler privilege escalation ·
- CVE-2021-22941, Citrix ShareFile: improper access control ·
- CVE-2020-9377, D-Link DIR-610 Devices: remote command execution ·
Every Sitecore flaw on CISA’s list · Everything added in March 2022
References
- ^ Cybersecurity and Infrastructure Security Agency. “Sitecore XP Remote Command Execution Vulnerability”. Known Exploited Vulnerabilities Catalog, added 25 Mar 2022.
- ^ National Institute of Standards and Technology. “CVE-2021-42237 Detail”. National Vulnerability Database, published 5 Nov 2021.
- ^ Sitecore. Advisories and fixes: support.sitecore.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.976, percentile 99.9, 31 Oct 2026.
- CVE Program. “CVE-2021-42237”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.