CVE-2011-2523

CRITICALNVD 9.89.8—
EchelonGraph scoreHIGH confidence

Score elevated to 9.8 because EPSS predicts 94% probability of exploitation within the next 30 days (top 0.1% of all CVEs). NVD baseline CVSS 9.8 retained for reference. Confidence: see factors.

Triggered by: EPSS exploit prediction ≥85%
Sources: epss, nvd
Weaponized
9.8
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 96%
CISA-KEV: Not listedEPSS: 96%CVSS: 9.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

vsftpd 2.3.4 downloaded between 20110630 and 20110703 contains a backdoor which opens a shell on port 6200/tcp.

CVSS v3
9.8
EG Score
9.8(high)
EPSS
99.9%
KEV
Not listed

Published

November 27, 2019

Last Modified

November 21, 2024

Advisory Details (4)

Auto-updated Jun 22, 2026
🔬 Proof of concept available. Patch available. Sources: redhat.
generic

CVE-2011-2523

https://security-tracker.debian.org/tracker/CVE-2011-2523
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/cve-2011-2523
generic

oss-security - Re: vsftpd download backdoored

https://www.openwall.com/lists/oss-security/2011/07/11/5
generic🟡 PoC Available

Vulnerability about vsftpd: backdoor in version 2.3.4 | Vigilance.fr

https://vigilance.fr/vulnerability/vsftpd-backdoor-in-version-2-3-4-10805

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 3× in last 7d / 9× 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. 2026-07-15 16:54 UTCEPSS rescore
  2. 2026-07-15 16:54 UTCEPSS rescore
  3. 2026-07-13 06:08 UTCEPSS rescore
  4. 2026-07-01 15:02 UTCEPSS rescore
  5. 2026-07-01 15:02 UTCEPSS rescore
  6. 2026-06-30 23:19 UTCEPSS rescore
  7. 2026-06-30 23:19 UTCEPSS rescore
  8. 2026-06-23 21:30 UTCEPSS rescore
  9. 2026-06-23 21:30 UTCEPSS rescore
  10. 2026-06-15 17:44 UTCEPSS rescore
  11. 2026-05-31 22:28 UTCEPSS rescore
  12. 2026-05-31 22:28 UTCEPSS rescore
  13. 2026-05-27 13:38 UTCEPSS rescore
  14. 2026-05-27 13:38 UTCEPSS rescore
  15. 2026-05-27 11:04 UTCEG score recompute
  16. 2026-05-27 11:04 UTCGHSA enrichment

Publicly available exploits

(10 references)

Working exploit code is in the public domain (8 GitHub PoCs) (2 Exploit-DB entries). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCBolivarJ/CVE-2011-2523
    First seen Aug 11, 2025

    Python exploit for vsftpd 2.3.4 - Backdoor Command Execution

    Open source ↗
  • GitHub PoCGill-Singh-A/vsFTP-2.3.4-Remote-Root-Shell-Exploit
    First seen Aug 3, 2024

    A Simple Python Program that uses gets a Remote Root Shell on the Target Device by exploiting a Vulnerability (CVE-2011-2523) present in vsFTP 2.3.4

    Open source ↗
  • GitHub PoC4m3rr0r/CVE-2011-2523-poc
    First seen Nov 28, 2023

    Python exploit for CVE-2011-2523 (VSFTPD 2.3.4 Backdoor Command Execution)

    Open source ↗
  • GitHub PoCLynk4/CVE-2011-2523
    First seen May 9, 2023

    Python exploit for vsftpd 2.3.4 - Backdoor Command Execution

    Open source ↗
  • GitHub PoCcowsecurity/CVE-2011-2523
    First seen Feb 5, 2023

    CVE-2011-2523 exploit

    Open source ↗
  • GitHub PoCMFernstrom/OffensivePascal-CVE-2011-2523
    First seen May 27, 2022

    FreePascal implementation of the vsFTPD 2.3.4 CVE-2011-2523

    Open source ↗
  • GitHub PoCpadsalatushal/CVE-2011-2523
    First seen Nov 7, 2021

    Python exploit for vsftpd 2.3.4 - Backdoor Command Execution

    Open source ↗
  • GitHub PoCnobodyatall648/CVE-2011-2523
    First seen May 1, 2021

    vsftpd 2.3.4 Backdoor Exploit

    Open source ↗
  • Exploit-DBEDB-49757✓ verified
    First seen Apr 12, 2021

    vsftpd 2.3.4 - Backdoor Command Execution

    Open source ↗
  • Exploit-DBEDB-17491✓ verified
    First seen Jul 5, 2011

    vsftpd 2.3.4 - Backdoor Command Execution (Metasploit)

    Open source ↗

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2011-2523?
CVE-2011-2523 is a critical vulnerability published on November 27, 2019. vsftpd 2.3.4 downloaded between 20110630 and 20110703 contains a backdoor which opens a shell on port 6200/tcp.
When was CVE-2011-2523 disclosed?
CVE-2011-2523 was first published in the National Vulnerability Database on November 27, 2019, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2011-2523 actively exploited?
CVE-2011-2523 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 99.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2011-2523?
CVE-2011-2523 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2011-2523?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2011-2523, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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