vsftpd 2.3.4 downloaded between 20110630 and 20110703 contains a backdoor which opens a shell on port 6200/tcp.
CVE-2011-2523
“—” beside the score: it is equal to NVD's CVSS score.
This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 96% (99th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.
Also known asEUVD-2011-2508 (ENISA EUVD) · GHSA-qf3g-hgw2-8r8h (GitHub Security Advisories)Source: ENISA EUVD
- High exploitation likelihood — EPSS 96%
- Public exploit code is available (Metasploit, Exploit-DB, marked verified by Exploit-DB, other public proof-of-concept code)
No fix has been recorded since the CVE record was published in 2019 — if the vendor still supports the product, apply the fixed version it names; if not, isolate the affected system (restrict network access to it, for example with a firewall, or keep it off the internet) or retire the product.
- CVSS v3
- 9.8
- EG Score
- 9.8CRITICALmedium confidence
- EG Risk
- 83EG Risk 83/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity98% × 45%Impact severity (EG Severity): CVSS 9.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation96% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.Automatability0% × 15%CISA's BOD 26-04 default: no one has published Automatable for this CVE, and CISA treats it as “no” for a CVE not in KEV.SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.Exploitation public PoC (exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: No fix has been recorded since the CVE record was published in 2019. If the vendor still supports the product, apply the fixed version it names within your standard update timelines at low or medium mission impact and sooner than that at high; if it no longer does, isolate the affected system (restrict network access to it, for example with a firewall, or keep it off the internet) on your normal schedule at low or medium mission impact and sooner than that at high, or retire the product. - EPSS PROB
- 96%
- EPSS %ILE
- 99th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (9.8): severity, escalated by confirmed exploitation. This CVE's 9.8 is its impact severity (EG Severity), not escalated.
- EG Severity
- 9.8 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
- EG Likelihood
- 96% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-02). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track* at medium mission impactTrack at low, Track* at medium and Attend at high mission impact.CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says. In the directive's words, “Fix on system upgrade” means that, “unless conditions change”, the vulnerability “should be remediated the next time the vulnerable asset receives a scheduled major upgrade or rebuild”: its timelines are “dynamic as facts change”, and a KEV listing shortens them.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low, Track* at medium and Attend at high mission impact.
No fix has been recorded since the CVE record was published in 2019. If the vendor still supports the product, apply the fixed version it names within your standard update timelines at low or medium mission impact and sooner than that at high; if it no longer does, isolate the affected system (restrict network access to it, for example with a firewall, or keep it off the internet) on your normal schedule at low or medium mission impact and sooner than that at high, or retire the product.
Exploitation public PoC (exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says. In the directive's words, “Fix on system upgrade” means that, “unless conditions change”, the vulnerability “should be remediated the next time the vulnerable asset receives a scheduled major upgrade or rebuild”: its timelines are “dynamic as facts change”, and a KEV listing shortens them.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
November 27, 2019
Last Modified
November 21, 2024
Advisory Details (6)
Auto-updated Oct 7, 2026Packet Storm
https://packetstormsecurity.com/files/102745/VSFTPD-2.3.4-Backdoor-Command-Execution.htmlCVE-2011-2523 - Red Hat Customer Portal
Affected: Red Hat Enterprise Linux 3, 4, 5, or 6.
https://access.redhat.com/security/cve/cve-2011-2523Packet Storm
http://packetstormsecurity.com/files/162145/vsftpd-2.3.4-Backdoor-Command-Execution.htmloss-security - Re: vsftpd download backdoored
https://www.openwall.com/lists/oss-security/2011/07/11/5Vulnerability about vsftpd: backdoor in version 2.3.4 | Vigilance.fr
https://vigilance.fr/vulnerability/vsftpd-backdoor-in-version-2-3-4-10805Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 15× in last 7d / 52× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 6 repeat rows among the latest 77 are merged into the row they repeat.
- 2026-11-02 22:41 UTCEG score recompute
- 2026-11-02 22:41 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-11-01 23:41 UTCEG score recompute
- 2026-11-01 23:41 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-11-01 00:51 UTCEG score recompute
- 2026-11-01 00:51 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-31 02:01 UTCEG score recompute
- 2026-10-31 02:01 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-30 16:26 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-10-30 03:11 UTCEG score recompute
- 2026-10-30 03:11 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-29 04:22 UTCEG score recompute
- 2026-10-29 04:21 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-28 05:27 UTCEG score recompute
- 2026-10-28 05:27 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-27 06:38 UTCEG score recompute
- 2026-10-27 06:38 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-26 04:10 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-25 20:15 UTCEG score recompute
- 2026-10-25 16:26 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-10-25 05:20 UTCEG score recompute
- 2026-10-25 05:20 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-24 06:30 UTCEG score recompute
- 2026-10-24 06:30 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-23 07:39 UTCEG score recompute
Show 46 moreShow fewer
- 2026-10-23 07:39 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-22 08:48 UTCEG score recompute
- 2026-10-22 08:48 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-21 16:26 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-10-21 09:58 UTCEG score recompute
- 2026-10-21 09:58 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-20 11:08 UTCEG score recompute
- 2026-10-20 11:07 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-19 12:16 UTCEG score recompute
- 2026-10-19 12:16 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-18 10:28 UTCEG score recompute
- 2026-10-18 10:28 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-17 11:36 UTCEG score recompute
- 2026-10-17 11:35 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-16 12:43 UTCEG score recompute
- 2026-10-16 12:43 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-15 13:49 UTCEG score recompute
- 2026-10-15 13:48 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-14 16:26 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-10-14 08:43 UTCEG score recompute
- 2026-10-14 08:43 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-13 03:55 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-12 21:36 UTCEG score recompute
- 2026-10-12 05:05 UTCEG score recompute
- 2026-10-12 05:05 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-10-11 19:11 UTCEG score recompute
- 2026-10-11 19:11 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
- 2026-09-29 08:18 UTCEG score recompute
- 2026-09-24 13:57 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-09-12 14:54 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-09-06 13:41 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-09-05 15:22 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-07-23 01:05 UTCEG score recompute
- 2026-07-23 00:09 UTCEG score recompute
- 2026-07-22 21:47 UTCEG score recompute
- 2026-07-22 14:03 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-07-15 16:54 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-07-13 06:08 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-07-01 15:02 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-06-30 23:19 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-06-23 21:30 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-06-15 17:44 UTCEPSS rescoreEPSS 96% · 99th percentile
- 2026-05-31 22:28 UTCEPSS rescoreEPSS 94% · 99th percentile
- 2026-05-27 13:38 UTCEPSS rescoreEPSS 94% · 99th percentile
- 2026-05-27 11:04 UTCEG score recompute
- 2026-05-27 11:04 UTCGHSA enrichmentGHSA-qf3g-hgw2-8r8h · GitHub severity HIGH
Publicly available exploits
(15 references, 10 shown)Public exploit code is referenced for this CVE (1 Metasploit module, 2 Exploit-DB entries, 11 GitHub PoCs), as is 1 Nuclei detection template. A detection template checks whether a system is affected; it is not necessarily exploit code. No fix has been recorded since the CVE record was published in 2019. If the vendor still supports the product, apply the fixed version it names; if it no longer does, isolate the affected system or retire the product.
- Exploit-DBEDB-49757✓ verifiedPublished Apr 12, 2021
vsftpd 2.3.4 - Backdoor Command Execution
Open source ↗ - Exploit-DBEDB-17491✓ verifiedPublished Jul 5, 2011
vsftpd 2.3.4 - Backdoor Command Execution (Metasploit)
Open source ↗ - Metasploitexploit/unix/ftp/vsftpd_234_backdoor✓ verifiedPublished Jul 4, 2011
VSFTPD 2.3.4 Backdoor Command Execution
Open source ↗ - GitHub PoCMaalfer/CVE-2011-2523-vsftpd-2.3.4-exploitPublished Nov 19, 2025
Exploit para explotar la vulnerabilidad CVE-2011-2523 presente en la versión 2.3.4 de vsftpd.
Open source ↗ - GitHub PoCMaalfer/vsftpd-2.3.4-exploitPublished Nov 19, 2025
Exploit para explotar la vulnerabilidad CVE-2011-2523 presente en la versión 2.3.4 de vsftpd.
Open source ↗ - GitHub PoCBolivarJ/CVE-2011-2523Published Aug 11, 2025
Python exploit for vsftpd 2.3.4 - Backdoor Command Execution
Open source ↗ - GitHub PoCvedpakhare/vsftpd-234-vuln-reportPublished Apr 5, 2025
Vulnerability assessment and exploitation of vsftpd 2.3.4 (CVE-2011-2523) using Metasploit. Full report and proof of root access included.
Open source ↗ - GitHub PoCGill-Singh-A/vsFTP-2.3.4-Remote-Root-Shell-ExploitPublished 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-pocPublished Nov 28, 2023
Python exploit for CVE-2011-2523 (VSFTPD 2.3.4 Backdoor Command Execution)
Open source ↗ - GitHub PoCLynk4/CVE-2011-2523Published May 9, 2023
Python exploit for vsftpd 2.3.4 - Backdoor Command Execution
Open source ↗
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Same CWE
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- CVE-2012-5693EG 8.8HIGH
- CVE-2012-5878EG 9.8EPSS p95CRITICAL
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- CVE-2013-1598EG 8.8EPSS p98HIGH
- CVE-2013-2612EG 9.8CRITICAL
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Frequently asked(5)
What is CVE-2011-2523?
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What is the CVSS score of CVE-2011-2523?
How do I remediate CVE-2011-2523?
Dependency Blast Radius
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