CVE-2009-2521

MEDIUMCVSS v2 · 5.05.0—
EchelonGraph scoreLOW confidence

This CVE was only ever scored under CVSS v2.0. NVD CVSS v2.0 base 5.0 — v2 rates that MEDIUM (v2 bands: LOW 0.0–3.9 / MEDIUM 4.0–6.9 / HIGH 7.0–10.0; v2 has no CRITICAL band). Vector AV:N/AC:L/Au:N/C:N/I:N/A:P. CVSS v2 is an older, coarser metric than v3.1/v4.0 (no Scope, no User Interaction, no Attack Requirements), so it is not directly comparable to a v3 or v4 score. NVD has never re-scored this record under v3. EPSS predicts 82.3% exploitation probability in the next 30 days, which is reflected in EG Risk but does not lift the v2 base. Confidence: LOW.

Triggered by: NVD CVSS v2.0 (legacy fallback)
Sources: epss, nvd_v2
Weaponized
5.0EG
EchelonGraph verdictMitigate this weekExploitation is likely or a public exploit exists.
  • 311 internet-facing services (distinct ip:port) on record running an affected version — derived from Shodan data (© Shodan); a patched service can stay counted while its port stays open
  • High exploitation likelihood — EPSS 82%
  • Public exploit code is available (Metasploit, Exploit-DB (verified), epss top5pct, epss high, public exploit)
CISA-KEV: Not listedEPSS PROB: 82%CVSS v2: 5.0Exploit: Metasploit · Exploit-DB (verified) · epss top5pct · epss high · public exploitExposed services: 311

A fix is referenced (a reference tagged "Patch", often a source commit), but no release containing it is confirmed — find the release that contains it; until it is applied, mitigate (WAF / firewall / segmentation).

Stack consumption vulnerability in the FTP Service in Microsoft Internet Information Services (IIS) 5.0 through 7.0 allows remote authenticated users to cause a denial of service (daemon crash) via a list (ls) -R command containing a wildcard that references a subdirectory, followed by a .. (dot dot), aka "IIS FTP Service DoS Vulnerability."

Internet exposure · derived from Shodan data

311 internet-facing services (distinct ip:port) on record running a version that maps to CVE-2009-2521, in our KEV-Exposure radar’s Shodan-derived sample.

across 38 countries (United States, China, Italy, Spain, Canada)top: internet_information_services
See the KEV-Exposure radar →Derived from Shodan data. Shodan data is owned by Shodan, which holds its copyright (© Shodan). EchelonGraph claims no ownership of it or copyright in it. Aggregate, host-redacted.

How it counts: every 12 hours, when Shodan query credits allow, the radar runs one Shodan query per tracked product, reads up to 100 ip:port services per query, and keeps a service when its banner version matches a CISA-KEV or high-EPSS CVE; a service is dropped when neither a search nor a Shodan InternetDB port re-check has refreshed it for 21 days. A re-check that finds the port still listed by Shodan InternetDB refreshes the service without re-reading the banner, so a patched service can stay counted while its port stays open. A count is a banner-version inference over a sample, not an exploit test and not an internet-wide census, and the unit is a service, not a machine: a machine answering on two ports counts twice.

CVSS v2.0 (legacy)
5.0MEDIUMNVD never assigned a CVSS v3 rating to this CVE
EG Score
5.0MEDIUMlow confidence
EG Risk
60
EG Risk 60/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity50% × 45%
Exploitation82% × 40%
Automatability30% × 15%
CISA SSVC: Track at low, Track or Track* at medium and Track* or Attend at high mission impact.
Action: A fix is referenced, but no release containing it is confirmed. Check the referenced fix and the vendor's advisory for a release that contains it and apply that within your standard update timelines at low or medium mission impact and sooner than that at high; until then, restrict network exposure of the affected system or apply the vendor's mitigation.
EPSS PROB
82%
EPSS %ILE
99th
KEV
Not listed

CISA SSVCTrack at low, Track or Track* at medium and Track* or Attend at high mission impact.

A fix is referenced, but no release containing it is confirmed. Check the referenced fix and the vendor's advisory for a release that contains it and apply that within your standard update timelines at low or medium mission impact and sooner than that at high; until then, restrict network exposure of the affected system or apply the vendor's mitigation.

Exploitation public PoC (EG-KEV: weaponized) · Automatable unknown (not published for this CVE) · Technical impact unknown (not published for this CVE). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 4, 2009

Last Modified

April 23, 2026

References (10)

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 2× in last 7d / 8× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-07 23:37 UTCEPSS rescore
  2. 2026-10-05 17:37 UTCEPSS rescore
  3. 2026-09-30 14:58 UTCEPSS rescore
  4. 2026-09-29 07:59 UTCEG score recompute
  5. 2026-09-26 15:52 UTCEPSS rescore
  6. 2026-09-24 13:57 UTCEPSS rescore
  7. 2026-09-12 14:54 UTCEPSS rescore
  8. 2026-09-10 09:24 UTCEPSS rescore
  9. 2026-09-06 13:41 UTCEPSS rescore
  10. 2026-09-05 15:22 UTCEPSS rescore
  11. 2026-08-28 21:34 UTCEPSS rescore
  12. 2026-08-19 16:58 UTCEPSS rescore
  13. 2026-08-15 01:24 UTCEPSS rescore
  14. 2026-08-08 16:31 UTCEPSS rescore
  15. 2026-08-06 13:41 UTCEPSS rescore
  16. 2026-07-30 01:26 UTCEPSS rescore
  17. 2026-07-26 13:38 UTCEG score recompute▲ 5.00
  18. 2026-07-25 14:12 UTCEPSS rescore
  19. 2026-07-24 14:12 UTCEPSS rescore
  20. 2026-07-23 00:59 UTCEG score recompute
  21. 2026-07-23 00:37 UTCEG score recompute▼ 8.60
  22. 2026-07-23 00:04 UTCEG score recompute▲ 8.60
  23. 2026-07-22 21:43 UTCEG score recompute
  24. 2026-07-22 14:03 UTCEPSS rescore
  25. 2026-07-21 15:20 UTCEPSS rescore
Show 58 more
  1. 2026-07-20 17:03 UTCEPSS rescore
  2. 2026-07-20 17:03 UTCEPSS rescore
  3. 2026-07-16 16:58 UTCEPSS rescore
  4. 2026-07-15 16:54 UTCEPSS rescore
  5. 2026-07-15 16:54 UTCEPSS rescore
  6. 2026-07-13 22:25 UTCEPSS rescore
  7. 2026-07-09 19:04 UTCEPSS rescore
  8. 2026-07-06 02:19 UTCEPSS rescore
  9. 2026-07-06 02:19 UTCEPSS rescore
  10. 2026-07-04 06:27 UTCEPSS rescore
  11. 2026-07-01 15:02 UTCEPSS rescore
  12. 2026-06-27 03:05 UTCEPSS rescore
  13. 2026-06-25 13:46 UTCEPSS rescore
  14. 2026-06-25 13:46 UTCEPSS rescore
  15. 2026-06-23 21:29 UTCEPSS rescore
  16. 2026-06-23 21:29 UTCEPSS rescore
  17. 2026-06-21 14:53 UTCEPSS rescore
  18. 2026-06-21 01:56 UTCEPSS rescore
  19. 2026-06-21 01:56 UTCEPSS rescore
  20. 2026-06-17 17:49 UTCEPSS rescore
  21. 2026-06-17 17:49 UTCEPSS rescore
  22. 2026-06-16 17:49 UTCEPSS rescore
  23. 2026-06-16 17:49 UTCEPSS rescore
  24. 2026-06-15 17:44 UTCEPSS rescore
  25. 2026-06-14 23:14 UTCEPSS rescore
  26. 2026-06-14 23:14 UTCEPSS rescore
  27. 2026-06-13 22:57 UTCEPSS rescore
  28. 2026-06-12 23:08 UTCEPSS rescore
  29. 2026-06-12 23:08 UTCEPSS rescore
  30. 2026-06-10 22:14 UTCEPSS rescore
  31. 2026-06-10 13:17 UTCEPSS rescore
  32. 2026-06-08 14:13 UTCEPSS rescore
  33. 2026-06-07 15:22 UTCEPSS rescore
  34. 2026-06-07 15:22 UTCEPSS rescore
  35. 2026-06-06 13:44 UTCEPSS rescore
  36. 2026-06-06 13:44 UTCEPSS rescore
  37. 2026-06-06 13:44 UTCEPSS rescore
  38. 2026-06-05 22:44 UTCEPSS rescore
  39. 2026-06-05 22:44 UTCEPSS rescore
  40. 2026-06-05 06:07 UTCEPSS rescore
  41. 2026-06-02 20:10 UTCEPSS rescore
  42. 2026-06-02 20:10 UTCEPSS rescore
  43. 2026-06-01 13:49 UTCEPSS rescore
  44. 2026-06-01 13:49 UTCEPSS rescore
  45. 2026-05-31 00:13 UTCEPSS rescore
  46. 2026-05-31 00:13 UTCEPSS rescore
  47. 2026-05-30 15:28 UTCEG score recompute
  48. 2026-05-30 15:28 UTCGHSA enrichment
  49. 2026-05-29 13:40 UTCEPSS rescore
  50. 2026-05-28 13:42 UTCEPSS rescore
  51. 2026-05-28 13:42 UTCEPSS rescore
  52. 2026-05-28 13:42 UTCEPSS rescore
  53. 2026-05-27 13:38 UTCEPSS rescore
  54. 2026-05-27 13:38 UTCEPSS rescore
  55. 2026-05-24 16:43 UTCEPSS rescore
  56. 2026-05-22 21:15 UTCEPSS rescore
  57. 2026-05-22 21:15 UTCEPSS rescore
  58. 2026-05-18 21:29 UTCEPSS rescore

Publicly available exploits

(3 references)

Working exploit code is in the public domain (1 Metasploit module) (2 Exploit-DB entries). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Exploit-DBEDB-9587✓ verified
    First seen Sep 4, 2009

    Microsoft IIS 5.0/6.0 FTP Server - Stack Exhaustion Denial of Service

    Open source ↗
  • Metasploitauxiliary/dos/windows/ftp/iis_list_exhaustion✓ verified
    First seen Sep 3, 2009

    Microsoft IIS FTP Server LIST Stack Exhaustion

    Open source ↗
  • Exploit-DBEDB-17476
    First seen Jul 3, 2011

    Microsoft IIS 7.0 FTP Server - Stack Exhaustion Denial of Service (MS09-053) (Metasploit)

    Open source ↗

Related CVEs(same CWE)

Frequently asked(4)

What is CVE-2009-2521?
CVE-2009-2521 is a medium vulnerability published on September 4, 2009. Stack consumption vulnerability in the FTP Service in Microsoft Internet Information Services (IIS) 5.0 through 7.0 allows remote authenticated users to cause a denial of service (daemon crash) via a list (ls) -R command containing a wildcard that references a subdirectory, followed by a .. (dot…
When was CVE-2009-2521 disclosed?
CVE-2009-2521 was first published on September 4, 2009, with the most recent update on April 23, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2009-2521 actively exploited?
CVE-2009-2521 is not currently on CISA's Known Exploited Vulnerabilities catalog. EchelonGraph's EG-KEV model classifies it as weaponized: a functional public exploit exists. FIRST EPSS estimates a 82% probability of exploitation in the next 30 days (99th percentile of EPSS-scored CVEs).
How do I remediate CVE-2009-2521?
A fix for CVE-2009-2521 is referenced (a reference tagged "Patch", often a source commit), but EchelonGraph has no release containing it on record. Check that reference and the vendor's advisory for a release that contains the fix and update to it; until then, restrict network exposure of the affected system or apply the vendor's mitigation.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2009-2521

Explore →

Is Your Infrastructure Affected by CVE-2009-2521?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Book a Demo →Browse All CVEs