CVE-2026-67248: ADM File Explorer Buffer Overflow Flaw

CVE-2026-67248 Overview

CVE-2026-67248 is a stack-based buffer overflow vulnerability in the File Explorer component of Asustor Data Master (ADM). The flaw exists in a Common Gateway Interface (CGI) process that decodes user-controlled input and copies it into a fixed-size stack buffer without proper length validation. An authenticated attacker with network access can trigger the overflow to crash the affected CGI process, resulting in denial of service. Depending on runtime protections and exploitability, further impact such as memory corruption or code execution may be possible. The vulnerability is tracked under CWE-121 (Stack-based Buffer Overflow).

Critical Impact
Authenticated attackers can crash the File Explorer CGI process and potentially achieve further memory corruption on affected ADM releases.

Affected Products

Asustor ADM 4.1.0 through 4.3.3.RUN1
Asustor ADM 5.0.0 through 5.1.3.RI81
Asustor Network Attached Storage (NAS) devices running affected ADM firmware

Discovery Timeline

2026-07-30 - CVE-2026-67248 published to the National Vulnerability Database (NVD)
2026-07-30 - Last updated in NVD database

Technical Details for CVE-2026-67248

Vulnerability Analysis

The vulnerability resides in the File Explorer CGI handler shipped with Asustor ADM. The handler accepts encoded input from authenticated users, decodes it, and writes the decoded bytes into a fixed-size buffer allocated on the stack. Because the decoded length is not checked against the size of the destination buffer, an attacker can supply an oversized payload that writes past the buffer boundary. Writing beyond the buffer overwrites adjacent stack data, including saved registers and the return address of the current function.

The immediate outcome is corruption of the CGI process control flow, leading to a crash. Depending on stack protections such as canaries, Address Space Layout Randomization (ASLR), and non-executable stacks, an attacker may be able to escalate the impact from denial of service toward arbitrary code execution within the CGI process context. Exploitation requires valid authentication to the ADM interface but no user interaction beyond that.

Root Cause

The root cause is missing bounds validation on decoded user input prior to a copy operation into a stack-allocated buffer. The affected code path processes attacker-controlled data through a decoding routine and passes the result directly to a copy primitive without verifying that the decoded length fits the destination. This pattern maps to CWE-121, stack-based buffer overflow.

Attack Vector

The attack is delivered over the network against the ADM web management interface. An authenticated attacker sends a crafted HTTP request to the File Explorer CGI endpoint containing an encoded payload larger than the target stack buffer expects after decoding. The CGI process decodes the payload, overflows the buffer, and either crashes or executes attacker-influenced instructions.

No verified proof-of-concept code is publicly available. Refer to the Asustor Security Advisory #69 for vendor-supplied technical context.

Detection Methods for CVE-2026-67248

Indicators of Compromise

Unexpected crashes or restarts of the File Explorer CGI process on Asustor NAS devices.
HTTP requests to File Explorer CGI endpoints containing unusually long or malformed encoded parameters.
Core dumps or segmentation fault entries in ADM system logs originating from the File Explorer handler.
Authenticated sessions issuing repeated File Explorer requests from unfamiliar source addresses.

Detection Strategies

Inspect ADM system and web server logs for repeated 5xx responses or process termination events tied to File Explorer CGI URIs.
Deploy web application firewall or intrusion detection rules that flag oversized parameter values sent to ADM File Explorer endpoints.
Correlate authentication events with subsequent CGI crashes to identify accounts being used to trigger the overflow.

Monitoring Recommendations

Enable verbose logging on the ADM web interface and forward logs to a centralized Security Information and Event Management (SIEM) platform for retention and analysis.
Monitor NAS device availability and CGI process health to detect denial-of-service conditions early.
Track authentication anomalies, including logins from new geographies or use of service accounts against the File Explorer interface.

How to Mitigate CVE-2026-67248

Immediate Actions Required

Upgrade Asustor ADM to a fixed release above 4.3.3.RUN1 in the 4.x branch or above 5.1.3.RI81 in the 5.x branch as published by the vendor.
Restrict administrative and File Explorer access to trusted management networks using firewall rules or VPN.
Audit ADM user accounts, disable unused accounts, and rotate credentials that may have been shared.
Enforce strong, unique passwords and enable multi-factor authentication where supported.

Patch Information

Asustor has released firmware updates addressing this vulnerability. Consult the Asustor Security Advisory #69 for the exact fixed versions and download links, then apply the update through the ADM update interface or by manual firmware installation.

Workarounds

Block internet exposure of the ADM web interface until the firmware update is applied.
Limit File Explorer access to a minimal set of authenticated users and roles.
Place NAS devices behind a reverse proxy or web application firewall that enforces request size limits on CGI parameters.
Isolate affected NAS devices on a segmented network to reduce lateral movement risk in the event of successful exploitation.

bash

# Configuration example: restrict ADM web access at the network edge
# Replace 10.0.0.0/24 with your trusted management subnet
iptables -A INPUT -p tcp --dport 8000 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8000 -j DROP
iptables -A INPUT -p tcp --dport 8001 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8001 -j DROP