CVE-2021-30047: VSFTPD 3.0.3 allows attackers to cause a denial of service due to limited number of connections allowed.

Q: How do I fix CVE-2021-30047?

vsftpd: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-30047 being exploited?

CVE-2021-30047 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-2021-30047 affect?

CVE-2021-30047 affects vsftpd. Severity is high (CVSS 7.5). VSFTPD 3.0.3 allows attackers to cause a denial of service due to limited number of connections allowed.

Q: How urgent is CVE-2021-30047?

Priority 58/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEDOWNGRADE

CVE-2021-30047 is a high-severity flaw (CVSS 7.5) affecting vsftpd. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

VSFTPD 3.0.3 allows attackers to cause a denial of service due to limited number of connections allowed.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	3.2% (top 12%)
CISA exploited list	No
Published	2023-08-22
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: vsftpd project

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

Am I affected?

Timeline

2023-08-22 19:16 UTCPublished CVE record published
2026-06-17 03:49 UTCUpdated Record last modified

vsftpd project vsftpd DOWNGRADE

Affected: 3.0.3

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.0.3

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 3.0.3 (Debian / Ubuntu)

apt-cache madison vsftpd sudo apt install vsftpd=<VERSION_BEFORE_3.0.3> sudo apt-mark hold vsftpd

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list vsftpd sudo dnf downgrade vsftpd-<VERSION_BEFORE_3.0.3> sudo dnf versionlock add vsftpd

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Public exploits and detection

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

Nuclei scan template: vsftpd < 3.0.3 - DoS

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-2021-30047?

vsftpd: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-30047 being exploited?

CVE-2021-30047 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-2021-30047 affect?

CVE-2021-30047 affects vsftpd. Severity is high (CVSS 7.5). VSFTPD 3.0.3 allows attackers to cause a denial of service due to limited number of connections allowed.

How urgent is CVE-2021-30047?

Priority 58/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

vsftpd vulnerabilities

References

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