CVE-2021-27852: Checkbox Survey Deserialization of Untrusted Data Vulnerability

Q: How do I fix CVE-2021-27852?

survey: upgrade to 7.0. Exact commands for each OS are on this page.

Q: Is CVE-2021-27852 being exploited?

Yes. CVE-2021-27852 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

Q: What does CVE-2021-27852 affect?

CVE-2021-27852 affects survey. Severity is critical (CVSS 9.8). 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.

Q: How urgent is CVE-2021-27852?

Priority 92/100. Critical severity; EPSS top 2%: very likely to be exploited; Exploited in the wild (CISA KEV); CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Patch now

CRITICAL 9.8EXPLOITEDREMOTEUPGRADE

CVE-2021-27852 is a critical-severity flaw (CVSS 9.8) affecting survey, reported as exploited in the wild. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Critical severity
EPSS top 2%: very likely to be exploited
Exploited in the wild (CISA KEV)
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	30.3% (top 2%)
CISA exploited list	Yes, fix due 2022-05-02
Weakness	CWE-502
Published	2021-05-27
Last modified	2026-06-17

Publisher (CNA): CERT/CC · Vendor: checkbox

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-05-27 21:15 UTCPublished CVE record published
2022-04-11Exploited Added to the CISA Known Exploited Vulnerabilities list
2022-05-02Deadline CISA due date for US federal agencies to patch
2026-06-17 03:45 UTCUpdated Record last modified

checkbox survey UPGRADE

Affected: < 7.0

Fixed in: 7.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy survey || rpm -q survey || survey --version

2. UPGRADE to 7.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade survey

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade survey

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Exact fixes by distribution

Fedora 46 · bitcoin-core-selinux · FIXED · 0.3-2.fc46 · FEDORA-2026-51fc806272 · source

sudo dnf upgrade --advisory=FEDORA-2026-51fc806272

Fedora ELN · guestfs-tools · FIXED · 1.57.5-1.eln159 · FEDORA-2026-9577c5ec16 · source

sudo dnf upgrade --advisory=FEDORA-2026-9577c5ec16

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: www.kb.cert.org/vuls/id/706695

Verify at the official source NVD · CVE Program · CISA KEV catalog · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-27852?

survey: upgrade to 7.0. Exact commands for each OS are on this page.

Is CVE-2021-27852 being exploited?

Yes. CVE-2021-27852 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

What does CVE-2021-27852 affect?

CVE-2021-27852 affects survey. Severity is critical (CVSS 9.8). 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.

How urgent is CVE-2021-27852?

Priority 92/100. Critical severity; EPSS top 2%: very likely to be exploited; Exploited in the wild (CISA KEV); CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Related CVEs

CVE-2023-38057 MEDIUM 4.1 UPGRADE An improper input validation vulnerability in OTRS Survey modules allows any attacker with a link to a valid a
CVE-2021-21434 LOW 3.5 UPGRADE Survey administrator can craft a survey in such way that malicious code can be executed in the agent interface

References

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