CVE-2026-12174: D-Link DCS-935L Firmware RCE Vulnerability

CVE-2026-12174 Overview

A format string vulnerability affects the D-Link DCS-935L network camera running firmware version 1.10.01. The flaw resides in the snprintf function call within the /web/cgi-bin/greece/rhea endpoint of the HTTP handler component. Attackers can manipulate the data argument to trigger format string processing on attacker-controlled input. The vulnerability is remotely exploitable over the network and requires low privileges. Public disclosure of the issue increases the risk of opportunistic exploitation against exposed devices. The weakness is classified under [CWE-119], reflecting improper restriction of operations within memory buffer bounds.

Critical Impact
Remote attackers with low privileges can exploit the format string flaw to disclose memory contents, corrupt memory, or potentially execute arbitrary code on affected D-Link DCS-935L cameras.

Affected Products

D-Link DCS-935L hardware (all revisions covered by affected firmware)
D-Link DCS-935L firmware version 1.10.01
HTTP Handler component exposing /web/cgi-bin/greece/rhea

Discovery Timeline

2026-06-13 - CVE-2026-12174 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2026-12174

Vulnerability Analysis

The vulnerability is a format string flaw in the HTTP handler of the D-Link DCS-935L IP camera. Attacker-supplied input from the data parameter reaches a snprintf call inside the /web/cgi-bin/greece/rhea CGI binary without sanitization. Because the input is used as the format specifier argument rather than as a parameter to a fixed format string, format directives such as %x, %s, and %n are interpreted at runtime. The vulnerability is reachable over the network and requires only low privileges on the device's web interface. Successful exploitation can yield high impact across confidentiality, integrity, and availability of the camera. The EPSS probability is 0.997% with a percentile of 58.158, indicating a non-trivial likelihood of exploitation activity.

Root Cause

The root cause is the unsafe use of user-controlled data as the format string argument to snprintf. Secure practice requires a constant format specifier such as snprintf(buf, len, "%s", data) instead of snprintf(buf, len, data). Passing untrusted input directly causes the C library to parse format conversion specifiers from attacker-controlled bytes, violating memory safety guarantees described by [CWE-119].

Attack Vector

An authenticated attacker with low-privilege access to the camera's web interface sends a crafted HTTP request to /web/cgi-bin/greece/rhea with format specifiers embedded in the data parameter. The snprintf call processes these specifiers, allowing the attacker to read process memory through directives like %x and %s, or to corrupt memory via %n. The exploit has been disclosed publicly. No verified exploit code is included here; refer to the GitHub CVE Report and VulDB CVE-2026-12174 for technical details.

Detection Methods for CVE-2026-12174

Indicators of Compromise

HTTP requests to /web/cgi-bin/greece/rhea containing format specifier sequences such as %x, %s, %n, or %p within the data parameter
Unexpected camera reboots, web service crashes, or httpd process restarts on DCS-935L devices
Outbound connections from the camera to unfamiliar destinations following anomalous HTTP traffic
Authentication events from unusual source IP addresses preceding requests to the rhea endpoint

Detection Strategies

Inspect web server and reverse-proxy logs for URI patterns containing /greece/rhea combined with % characters in query strings or POST bodies.
Deploy network intrusion detection signatures that flag format specifier characters in HTTP parameters destined for embedded camera management interfaces.
Correlate failed or anomalous authentication attempts against IoT devices with subsequent requests to vulnerable CGI endpoints.

Monitoring Recommendations

Centralize syslog and HTTP access logs from D-Link cameras into a SIEM and alert on format specifier patterns in request parameters.
Monitor network segments hosting IoT and surveillance devices for unsolicited inbound HTTP traffic from the public internet.
Track firmware versions across deployed DCS-935L units and alert when devices remain on firmware 1.10.01.

How to Mitigate CVE-2026-12174

Immediate Actions Required

Remove direct internet exposure of D-Link DCS-935L management interfaces and place the cameras behind a firewall or VPN.
Restrict access to the web management interface to a dedicated administrative VLAN with allowlisted source IP addresses.
Rotate all administrative credentials on affected cameras and disable unused web accounts.
Audit deployed inventory for DCS-935L devices running firmware 1.10.01 and prioritize them for replacement or isolation.

Patch Information

No vendor advisory or patched firmware release for CVE-2026-12174 is referenced in the available data. The DCS-935L is a legacy product line. Consult the D-Link Official Website for current support status and replacement guidance. If no patch is forthcoming, plan device decommissioning.

Workarounds

Block external access to TCP ports used by the camera's HTTP service at the perimeter firewall.
Disable remote management features and any cloud connectivity options on the device when not required.
Segment IP cameras onto an isolated network with no routing to sensitive corporate resources.
Replace end-of-support DCS-935L units with currently supported camera models that receive security updates.

bash

# Example firewall rule to restrict access to camera management interface
iptables -A FORWARD -p tcp -d <camera_ip> --dport 80 -s <admin_subnet> -j ACCEPT
iptables -A FORWARD -p tcp -d <camera_ip> --dport 80 -j DROP
iptables -A FORWARD -p tcp -d <camera_ip> --dport 443 -s <admin_subnet> -j ACCEPT
iptables -A FORWARD -p tcp -d <camera_ip> --dport 443 -j DROP