CVE-2026-1951: Delta Electronics AS320T Buffer Overflow

CVE-2026-1951 Overview

A stack-based buffer overflow vulnerability exists in Delta Electronics AS320T NAS devices due to improper validation of directory name buffer lengths. This flaw allows remote attackers to potentially execute arbitrary code or cause denial of service by sending specially crafted requests with oversized directory names to the affected device.

Critical Impact

This vulnerability enables unauthenticated remote attackers to exploit memory corruption in Delta Electronics AS320T devices, potentially leading to complete system compromise with full read, write, and execute capabilities.

Affected Products

• Delta Electronics AS320T NAS devices

Discovery Timeline

• April 24, 2026 - CVE-2026-1951 published to NVD
• April 24, 2026 - Last updated in NVD database

Technical Details for CVE-2026-1951

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), a memory corruption flaw that occurs when input data exceeds the allocated stack buffer boundaries. The Delta Electronics AS320T fails to perform adequate length validation on directory name inputs before copying them into a fixed-size stack buffer. When an attacker provides a directory name that exceeds the expected buffer size, the excess data overwrites adjacent memory on the stack, including return addresses and saved registers.

The network-accessible nature of this vulnerability means attackers can exploit it remotely without requiring authentication or user interaction. Successful exploitation could allow an attacker to hijack program execution flow, inject malicious code, and gain complete control over the affected NAS device.

Root Cause

The root cause of this vulnerability is the absence of boundary checking when processing directory name inputs. The application allocates a fixed-size buffer on the stack for storing directory names but does not verify that incoming data fits within this allocation before performing copy operations. This classic programming error enables stack smashing attacks where carefully crafted input can overwrite critical stack data structures.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker can craft malicious requests containing oversized directory name parameters and send them to the AS320T device's network-accessible services. When the vulnerable code processes these requests, the oversized directory name causes a buffer overflow condition.

The exploitation typically involves:

1. Identifying the exact buffer size allocated for directory names
2. Crafting a payload that fills the buffer and overwrites the return address
3. Redirecting execution to attacker-controlled code or gadgets
4. Achieving arbitrary code execution with the privileges of the vulnerable process

Due to the nature of this vulnerability, exploitation details are not provided. For technical analysis, refer to the Delta Security Advisory.

Detection Methods for CVE-2026-1951

Indicators of Compromise

• Unexpected crashes or service restarts on Delta Electronics AS320T devices
• Unusual network traffic patterns targeting AS320T management interfaces
• Evidence of abnormally long directory name strings in network logs or application logs
• Suspicious processes or unauthorized file modifications on the NAS device

Detection Strategies

• Monitor network traffic for HTTP/HTTPS requests containing unusually long directory path parameters destined for AS320T devices
• Implement intrusion detection system (IDS) rules to detect potential buffer overflow attempts targeting NAS devices
• Configure logging to capture and alert on directory name parameters exceeding normal operational lengths
• Deploy network segmentation to isolate NAS devices and monitor cross-segment communication anomalies

Monitoring Recommendations

• Enable verbose logging on AS320T devices if supported to capture detailed request information
• Monitor system resource utilization for signs of exploitation attempts such as CPU spikes or memory anomalies
• Review authentication logs for failed or suspicious access attempts preceding device instability
• Implement centralized log collection for AS320T devices to facilitate correlation and analysis

How to Mitigate CVE-2026-1951

Immediate Actions Required

• Review the Delta Security Advisory for official guidance and patches
• Restrict network access to AS320T devices using firewall rules, limiting exposure to trusted networks only
• Implement network segmentation to isolate NAS devices from untrusted network segments
• Monitor AS320T devices for signs of exploitation while awaiting vendor patches

Patch Information

Delta Electronics has published a security advisory addressing CVE-2026-1951 along with related vulnerabilities (CVE-2026-1949, CVE-2026-1950, CVE-2026-1952). Organizations should consult the Delta Security Advisory PCSA-2026-00006 for specific patch versions and installation instructions.

Workarounds

• Place AS320T devices behind a firewall that restricts access to management interfaces from untrusted networks
• Disable any unnecessary network services on the AS320T to reduce attack surface
• Implement access control lists (ACLs) to limit which IP addresses can communicate with the NAS device
• Consider temporarily taking affected devices offline if they cannot be adequately protected until patches are applied

# Example firewall rule to restrict AS320T access (adjust IP ranges as needed)
# Allow only trusted management network
iptables -A INPUT -p tcp -s 192.168.1.0/24 -d <AS320T_IP> --dport 80 -j ACCEPT
iptables -A INPUT -p tcp -s 192.168.1.0/24 -d <AS320T_IP> --dport 443 -j ACCEPT
# Block all other access to management ports
iptables -A INPUT -p tcp -d <AS320T_IP> --dport 80 -j DROP
iptables -A INPUT -p tcp -d <AS320T_IP> --dport 443 -j DROP