CVE-2025-14242: vsftpd Denial of Service Vulnerability

CVE-2025-14242 Overview

A vulnerability has been identified in vsftpd, the popular FTP server daemon. This flaw allows authenticated remote attackers to cause a denial of service (DoS) condition by exploiting an integer overflow in the ls command parameter parsing. The vulnerability is triggered when an attacker sends a specially crafted STAT command containing a specific byte sequence, causing the server to become unresponsive or crash.

Critical Impact

Authenticated attackers can remotely crash vsftpd servers, disrupting FTP services and potentially affecting business operations that rely on file transfer functionality.

Affected Products

• vsftpd (Very Secure FTP Daemon)
• Red Hat Enterprise Linux systems running vsftpd
• Linux distributions with affected vsftpd packages

Discovery Timeline

• January 14, 2026 - CVE-2025-14242 published to NVD
• January 14, 2026 - Last updated in NVD database

Technical Details for CVE-2025-14242

Vulnerability Analysis

This vulnerability is classified as CWE-190 (Integer Overflow or Wraparound). The flaw exists in the parameter parsing logic for the ls command within vsftpd. When processing directory listing requests via the STAT command, the server fails to properly validate integer boundaries, allowing an attacker to trigger an overflow condition.

The attack requires network access and valid authentication credentials to the FTP server. Once authenticated, an attacker can send a maliciously crafted STAT command with a specific byte sequence designed to overflow integer variables used in parameter parsing. This leads to unexpected behavior that results in service unavailability.

Root Cause

The root cause is insufficient bounds checking on integer values during the parsing of ls command parameters. When the vsftpd daemon processes certain input values, the integer arithmetic operations can overflow, wrapping around to unexpected values. This integer overflow corrupts the internal state of the application, leading to a denial of service condition.

Attack Vector

The attack is conducted over the network against an FTP server running a vulnerable version of vsftpd. The attacker must first authenticate to the server with valid credentials (low privilege required). Once authenticated, the attacker sends a specially crafted STAT command containing a byte sequence designed to trigger the integer overflow in the ls parameter parsing routine.

The vulnerability mechanism involves:

1. An authenticated user establishes an FTP session with the vsftpd server
2. The attacker sends a STAT command with specially crafted parameters
3. The server's ls command parameter parser attempts to process the input
4. Integer overflow occurs during arithmetic operations on the malicious input
5. The corrupted internal state causes the server process to crash or become unresponsive

For technical details regarding the specific byte sequence and exploitation mechanics, refer to the Red Hat Bugzilla Report #2419826.

Detection Methods for CVE-2025-14242

Indicators of Compromise

• Unexpected vsftpd service crashes or restarts in system logs
• Repeated STAT commands with abnormally long or unusual parameters in FTP access logs
• High volume of authentication attempts followed by specific command patterns from single sources
• Service unavailability reports coinciding with suspicious FTP activity

Detection Strategies

• Monitor FTP server logs for unusual STAT command patterns or malformed requests
• Implement intrusion detection rules to identify potential integer overflow exploitation attempts in FTP traffic
• Deploy SentinelOne Singularity XDR to detect anomalous process behavior and service crashes
• Configure alerting for repeated vsftpd service failures or unexpected daemon restarts

Monitoring Recommendations

• Enable verbose logging on vsftpd servers to capture detailed command history
• Implement network traffic analysis to identify suspicious FTP command sequences
• Configure centralized log collection for FTP servers to correlate potential attack patterns
• Set up availability monitoring with automatic alerts for vsftpd service interruptions

How to Mitigate CVE-2025-14242

Immediate Actions Required

• Apply the latest security patches from Red Hat or your Linux distribution vendor immediately
• Review FTP server access logs for signs of exploitation attempts
• Consider temporarily restricting FTP access to trusted IP addresses if patching is not immediately possible
• Audit user accounts with FTP access and disable any unnecessary accounts

Patch Information

Red Hat has released security advisories addressing this vulnerability. Organizations should apply the appropriate patches based on their Red Hat Enterprise Linux version:

• Red Hat Security Advisory RHSA-2026:0605
• Red Hat Security Advisory RHSA-2026:0606
• Red Hat Security Advisory RHSA-2026:0608

For detailed CVE analysis and affected package versions, refer to the Red Hat CVE Analysis for CVE-2025-14242.

Workarounds

• Implement network-level access controls to restrict FTP access to trusted IP ranges only
• Use firewall rules to limit connections to the FTP service from known, authorized sources
• Consider migrating to more secure file transfer protocols such as SFTP or SCP where possible
• Enable connection rate limiting to reduce the impact of potential exploitation attempts

# Example: Restrict FTP access using iptables
iptables -A INPUT -p tcp --dport 21 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 21 -j DROP

# Example: Configure vsftpd to limit connections
# Add to /etc/vsftpd/vsftpd.conf
max_clients=50
max_per_ip=5