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CVE-2011-2523

94
FAUCET Score

CVE-2011-2523 describes a critical backdoor vulnerability present in vsftpd version 2.3.4, specifically in builds downloaded between June 30 and July 3, 2011, affecting Debian Linux distributions. This flaw allows an unauthenticated attacker to execute arbitrary commands by opening a shell on TCP port 6200. With a CVSS score of 9.8 and an EPSS score indicating high exploitability, this vulnerability poses a severe risk, enabling complete compromise of confidentiality, integrity, and availability. While not listed in CISA's KEV catalog, multiple public exploit modules exist for Metasploit and Nuclei, confirming its ease of exploitation, despite minimal public discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
2.3.4CPE matchmatch criteria
cpe:2.3:a:vsftpd_project:vsftpd:2.3.4:*:*:*:*:*:*:*
8.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
96.18%
Probability of exploitation in next 30 days
EPSS Percentile
99.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-24
Model: v2026.06.15
Metasploit: VSFTPD 2.3.4 Backdoor Command Execution · Jul 3, 2011
Nuclei: CVE-2011-2523 · Mar 3, 2023
ExploitDB: EDB-49757 · Apr 12, 2021
This CVE's current EPSS score of 0.9618 is in the 99th percentile among its peer group of 36,821 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Advisories (1)

redhatCVE-2011-2523Important

vsftpd: backdoor which opens a shell on port 6200/tcp

Jul 4, 2011

References

packetstormsecurity.com / files/162145/vsftpd-2.3.4-Backdoor-Command-Execution.html
access.redhat.com / security/cve/cve-2011-2523
Third Party Advisory
packetstormsecurity.com / files/102745/VSFTPD-2.3.4-Backdoor-Command-Execution.html
ExploitThird Party AdvisoryVDB Entry
security-tracker.debian.org / tracker/CVE-2011-2523
Third Party Advisory
vigilance.fr / vulnerability/vsftpd-backdoor-in-version-2-3-4-10805
Third Party Advisory
openwall.com / lists/oss-security/2011/07/11/5
Mailing ListThird Party Advisory