CVE-2021-27852
CVE-2021-27852 is a security flaw in Checkbox Survey. Attackers can run their own code on Checkbox Survey 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 11 Apr 2022.[1]
Checkbox Survey 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. Fixed in version 7 of Survey.
Description
CISA calls it a survey deserialization of untrusted data in Checkbox Checkbox Survey. In its words: “Deserialization of Untrusted Data vulnerability in CheckboxWeb.dll of Checkbox Survey allows an unauthenticated remote attacker to execute arbitrary code.”[1]
The CVE record adds: “Deserialization of Untrusted Data vulnerability in CheckboxWeb.dll of Checkbox Survey allows an unauthenticated remote attacker to execute arbitrary code. This issue affects: Checkbox Survey versions prior to 7.”[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 lists one fixed version: everything before it is affected.[2]
| Product | Fixed in |
|---|---|
| Survey | 7 |
Most families won’t have Checkbox Survey; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 11 Apr 2022, 319 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 2 May 2022 to fix it.[1]
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 30%. That’s in the top 2% of the flaws it scores.[3]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
CISA’s required action: “Versions 6 and earlier for this product are end-of-life and must be removed from agency networks.”[1]
- Check whether you use it.Checkbox Survey 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 (fixed in version 7 of Survey), or not in use. CISA gave US government agencies until 2 May 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.[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 30%.[3] |
See also
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-2022-23176, WatchGuard Firebox and XTM: privilege escalation ·
- CVE-2021-42287, Microsoft Active Directory: domain services privilege escalation ·
- CVE-2021-42278, Microsoft Active Directory: domain services privilege escalation ·
- CVE-2021-39793, Google Pixel: out-of-bounds write ·
- CVE-2021-22600, Linux Kernel: privilege escalation ·
References
- ^ Cybersecurity and Infrastructure Security Agency. “Checkbox Survey Deserialization of Untrusted Data Vulnerability”. Known Exploited Vulnerabilities Catalog, added 11 Apr 2022.
- ^ National Institute of Standards and Technology. “CVE-2021-27852 Detail”. National Vulnerability Database, published 27 May 2021.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.303, percentile 98.2, 31 Oct 2026.
- CVE Program. “CVE-2021-27852”. 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.