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CVE-2011-2523· NVD / CVE Program· CNA redhat

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

CriticalCVSS 9.8 · v3.1—Weaponized No fix recorded
Published
Nov 27, 2019
Updated
Jun 16, 2026
EPSS
96.2% · 100th percentile
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Action score

68

This week

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CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
29 / 30 · 96.2%

Affected systems

VendorProduct
vsftpd projectvsftpd
debiandebian linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux10.0
  • debian debian linux8.0
  • debian debian linux9.0
  • vsftpd project vsftpd2.3.4

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

  • vsftpd vsftpd

    • 2.3.4 downloaded between 20110630 and 20110703affected

Same product

vsftpd project: all records

Other highest-scoring records for the same primary product.

  • CVE-2011-0762The vsf_filename_passes_filter function in ls.c in vsftpd before 2.3.3 allows remote authenticated users to cause a denial of service (CPU c
    38Monitor
  • CVE-2021-30047VSFTPD 3.0.3 allows attackers to cause a denial of service due to limited number of connections allowed.
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Evidence

  • Metasploit module ×1
  • Exploit-DB entry ×2
  • Nuclei detection template ×1
  • Proof-of-concept repository on GitHub ×50

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Exploit-DB entryremote2021-04-12
Exploit-DB entryremote2011-07-05
Metasploit moduleexploit/unix/ftp/vsftpd_234_backdoorVSFTPD 2.3.4 Backdoor Command Executionexploit2011-07-03
Nuclei detection templateNuclei template CVE-2011-2523 —
Proof-of-concept repository on GitHubstars:02021-04-09
Proof-of-concept repository on GitHubstars:32021-05-01
Proof-of-concept repository on GitHubstars:02021-08-31
Proof-of-concept repository on GitHubstars:152021-11-07
Proof-of-concept repository on GitHubstars:22022-05-27
Proof-of-concept repository on GitHubstars:02022-06-09
Proof-of-concept repository on GitHubstars:02022-06-09
Proof-of-concept repository on GitHubstars:02022-12-03

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Metasploit-3070 d
  2. First PoC-3068 d
  3. Published
  4. TodaySep 30, 2026+2499 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-78 · Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-primary

Root cause

User input is inserted as text into a shell command. The shell may interpret special characters in the input as part of the command.

The bug in code

The whole CWE-78 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
const host = req.body.host;exec("ping -c 1 " + host, onResult);

Fixed

ts
const host = req.body.host;if (!/^[a-z0-9.-]{1,253}$/i.test(host)) return res.sendStatus(400);execFile("ping", ["-c", "1", host], onResult);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

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Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records