CVE-2026-7834: ipTIME NAS1dual Buffer Overflow Flaw

CVE-2026-7834 Overview

CVE-2026-7834 is a stack-based buffer overflow vulnerability in EFM ipTIME NAS1dual firmware version 1.5.24. The flaw resides in the get_csrf_whites function within /cgi/advanced/misc_main.cgi. Attackers can trigger the overflow remotely without authentication or user interaction. The exploit has been disclosed publicly, and the vendor did not respond to disclosure attempts. The weakness is classified under [CWE-119], improper restriction of operations within the bounds of a memory buffer.

Critical Impact

Remote unauthenticated attackers can corrupt stack memory in the NAS web management interface, enabling arbitrary code execution and full device compromise.

Affected Products

• EFM ipTIME NAS1dual firmware version 1.5.24
• The get_csrf_whites function in /cgi/advanced/misc_main.cgi
• Network-attached storage devices exposing the affected web management interface

Discovery Timeline

• 2026-05-05 - CVE-2026-7834 published to NVD
• 2026-05-05 - Last updated in NVD database
• Vendor disclosure - EFM was contacted before public disclosure but did not respond

Technical Details for CVE-2026-7834

Vulnerability Analysis

The vulnerability exists in the get_csrf_whites function of the CGI binary /cgi/advanced/misc_main.cgi on the ipTIME NAS1dual device. The function processes CSRF (Cross-Site Request Forgery) whitelist input without proper bounds checking. Attacker-controlled input flows into a fixed-size stack buffer, allowing the adjacent saved return address and stack frame metadata to be overwritten.

The attack vector is network-based and requires no authentication or user interaction. Successful exploitation can pivot from memory corruption into arbitrary code execution within the context of the NAS web service, which typically runs with elevated privileges on embedded Linux systems.

Root Cause

The root cause is missing input length validation in get_csrf_whites before copying user-supplied data into a stack-allocated buffer. The CGI handler trusts request data parsed from the HTTP layer and writes it directly into the buffer using an unbounded copy operation. This pattern is a textbook [CWE-119] memory boundary violation common in embedded C code on resource-constrained NAS firmware.

Attack Vector

An attacker sends a crafted HTTP request to the /cgi/advanced/misc_main.cgi endpoint with an oversized parameter consumed by get_csrf_whites. Because the CGI is reachable from the network and does not require authentication, exploitation can be conducted directly against any internet-exposed or LAN-accessible NAS1dual device. Public disclosure of exploit details on GitHub IoT Vulnerability Documentation and VulDB Vulnerability #361113 increases the likelihood of opportunistic exploitation.

No verified exploit code is reproduced here. Refer to the linked technical references for proof-of-concept details.

Detection Methods for CVE-2026-7834

Indicators of Compromise

• HTTP requests to /cgi/advanced/misc_main.cgi containing unusually long parameter values targeting CSRF whitelist fields
• Unexpected crashes, restarts, or service interruptions in the NAS web management daemon
• Outbound connections from the NAS device to unknown external IPs following anomalous CGI requests
• New or modified processes spawned by the web server user on the NAS

Detection Strategies

• Inspect web server and reverse proxy logs for repeated requests to misc_main.cgi with abnormal payload sizes
• Deploy network intrusion detection signatures matching oversized POST or GET parameters destined for /cgi/advanced/misc_main.cgi
• Monitor for HTTP 5xx error spikes from the NAS device, which may indicate exploitation attempts causing process crashes

Monitoring Recommendations

• Forward NAS device syslog and HTTP access logs to a centralized SIEM for correlation against known exploitation patterns
• Alert on any administrative interface access from non-management network segments
• Track baseline request size distributions for the affected CGI and flag statistical outliers

How to Mitigate CVE-2026-7834

Immediate Actions Required

• Remove the ipTIME NAS1dual web management interface from any internet-facing exposure and restrict it to trusted management VLANs
• Place affected devices behind a network firewall or reverse proxy that enforces strict request size limits on CGI endpoints
• Audit the device for signs of prior compromise, including unexpected processes, modified configuration files, and unknown user accounts

Patch Information

No vendor patch is currently available. EFM did not respond to coordinated disclosure attempts documented by the reporter. Organizations using ipTIME NAS1dual 1.5.24 should treat the device as unpatched and apply compensating network controls until the vendor releases an updated firmware version. Consult VulDB Vulnerability #361113 for status updates.

Workarounds

• Block external access to TCP ports serving the NAS web management interface at the perimeter firewall
• Disable remote administration features on the NAS where supported by the device configuration
• Replace the affected device with a supported product if the vendor remains unresponsive and the NAS handles sensitive data
• Apply ACLs restricting access to /cgi/advanced/misc_main.cgi to a narrow set of administrative source IPs

# Example iptables rule restricting NAS web management to a management subnet
iptables -A INPUT -p tcp --dport 80 -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP