CVE-2021-44159: 4MOSAn GCB Doctor’s file upload function has improper user privilege control

Q: How do I fix CVE-2021-44159?

gcb doctor: upgrade to 2021-09-16. Exact commands for each OS are on this page.

Q: Is CVE-2021-44159 being exploited?

CVE-2021-44159 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-44159 affect?

CVE-2021-44159 affects gcb doctor. Severity is critical (CVSS 9.8). 4MOSAn GCB Doctor’s file upload function has improper user privilege control. A remote attacker can upload arbitrary files including webshell files without authentication and execute arbitrary code in order to perform arbitrary system opera

Q: How urgent is CVE-2021-44159?

Priority 62/100. Critical severity; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2021-44159 is a critical-severity flaw (CVSS 9.8) affecting gcb doctor. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

4MOSAn GCB Doctor’s file upload function has improper user privilege control. A remote attacker can upload arbitrary files including webshell files without authentication and execute arbitrary code in order to perform arbitrary system operations or deny of service attack.

Why this priority

Critical severity
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	3.5% (top 11%)
CISA exploited list	No
Weakness	CWE-434
Published	2021-12-20
Last modified	2026-06-17

Publisher (CNA): TWCERT/CC · Vendor: 4mosan

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

Am I affected?

Timeline

2021-12-20 03:15 UTCPublished CVE record published
2026-06-17 04:11 UTCUpdated Record last modified

4mosan gcb doctor UPGRADE

Affected: < 2021-09-16

Fixed in: 2021-09-16

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy gcb-doctor || rpm -q gcb-doctor || gcb-doctor --version

2. UPGRADE to 2021-09-16 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade gcb-doctor

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade gcb-doctor

Note

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

Verify at the official source NVD · CVE Program · 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-2021-44159?

gcb doctor: upgrade to 2021-09-16. Exact commands for each OS are on this page.

Is CVE-2021-44159 being exploited?

CVE-2021-44159 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-44159 affect?

CVE-2021-44159 affects gcb doctor. Severity is critical (CVSS 9.8). 4MOSAn GCB Doctor’s file upload function has improper user privilege control. A remote attacker can upload arbitrary files including webshell files without authentication and execute arbitrary code in order to perform arbitrary system opera

How urgent is CVE-2021-44159?

Priority 62/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2021-42338 CRITICAL 9.8 UPGRADE 4MOSAn GCB Doctor’s login page has improper validation of Cookie, which allows an unauthenticated remote attac

References

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