CVE-2021-47865

ProFTPD 1.3.7a - Remote Denial of Service

8.7 High

ProFTPD 1.3.7a contains a denial of service vulnerability that allows attackers to overwhelm the server by creating multiple simultaneous FTP connections. Attackers can repeatedly establish connections using threading to exhaust server connection limits and block legitimate user access.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: High

Exploit likelihood

0.60%Up 0.6 points since Jan 22, 2026

What each source reports

CVE List Score used 8.7

ProFTPD 1.3.7a - Remote Denial of Service

Record: CVE-2021-47865
CVSS 4.0: 8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-770
Updated: 2026-11-02

EUVDEUVD-2026-3621 8.7

Record: EUVD-2026-3621
CVSS 4.0: 8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-mf77-27mv-mhm4 8.7

ProFTPD 1.3.7a contains a denial of service vulnerability that allows attackers to overwhelm the...

Record: GHSA-mf77-27mv-mhm4
CVSS 4.0: 8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-770
Updated: 2026-11-02

NVD 8.7

Record: CVE-2021-47865
CVSS 4.0: 8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-770
Updated: 2026-11-02

OSVUBUNTU-CVE-2021-47865 8.7

Record: UBUNTU-CVE-2021-47865
CVSS 4.0: 8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

Affected products

proftpd

Affected packages

Affected packages
Package	Affected	Fixed
`proftpd-dfsg` Ubuntu:16.04:LTS	All versions, plus listed versions 1.3.5-21.3.5a-11.3.5a-1build11.3.5a-1ubuntu0.1	None known
`proftpd-dfsg` Ubuntu:18.04:LTS	All versions, plus listed versions 1.3.5d-11.3.5e-1build1	None known
`proftpd-dfsg` Ubuntu:20.04:LTS	All versions, plus listed versions 1.3.6-6build21.3.6c-11.3.6c-21.3.6c-2ubuntu0.1	None known
`proftpd-dfsg` Ubuntu:22.04:LTS	All versions, plus listed versions 1.3.7b+dfsg-11.3.7c+dfsg-1build11.3.7c+dfsg-1ubuntu0.1	None known
`proftpd-dfsg` Ubuntu:24.04:LTS	All versions, plus listed versions 1.3.8+dfsg-81.3.8.a+dfsg-11.3.8.b+dfsg-11.3.8.b+dfsg-1build11.3.8.b+dfsg-1build21.3.8.b+dfsg-1build31.3.8.b+dfsg-1ubuntu0.1	None known
`proftpd-dfsg` Ubuntu:25.10	All versions, plus listed versions 1.3.8.c+dfsg-21.3.8.c+dfsg-41.3.9~dfsg-3	None known
`proftpd-dfsg` Ubuntu:26.10	All versions, plus listed versions 1.3.9~dfsg-41.3.9b~dfsg-11.3.9d~dfsg-1	None known
`proftpd-dfsg` Ubuntu:26.04:LTS	All versions, plus listed versions 1.3.9~dfsg-31.3.9~dfsg-4	None known

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-47865 is a high vulnerability (CVSS 8.7) in Proftpd, published January 21, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.60%, the 48th percentile. No source names a fixed version.