CVE-2026-76859 Overview
CVE-2026-76859 is a sensitive information disclosure vulnerability affecting Netcore NR255-V routers running firmware version 1.5.130703. The flaw resides in the user_pass_show.cgi component, which exposes router credentials to authenticated low-privilege users through the ui_config_2.xml and misc.js resources. An attacker with limited account access on the device can retrieve administrator credentials, enabling full takeover of the router. The weakness is tracked as [CWE-522: Insufficiently Protected Credentials].
Critical Impact
Low-privilege attackers can disclose administrator router credentials over the network, resulting in complete compromise of the affected Netcore NR255-V device.
Affected Products
- Netcore NR255-V router
- Firmware version 1.5.130703
- user_pass_show.cgi web management component
Discovery Timeline
- 2026-09-15 - CVE-2026-76859 published to the National Vulnerability Database (NVD)
- 2026-09-17 - Last updated in NVD database
Technical Details for CVE-2026-76859
Vulnerability Analysis
The Netcore NR255-V web management interface exposes the user_pass_show.cgi endpoint alongside supporting resources ui_config_2.xml and misc.js. These components return administrative credential material to any authenticated session, without enforcing role-based access control checks. A low-privilege user who authenticates to the device can therefore retrieve credentials belonging to higher-privilege accounts.
Because the disclosure occurs through standard HTTP responses served by the router's built-in web interface, exploitation requires no memory corruption, no elevated shell, and no chained vulnerabilities. The classification under [CWE-522] reflects the storage and transmission of credentials without adequate protection or authorization. According to the Exploit Prediction Scoring System (EPSS), the current probability of exploitation activity is 0.345% at the 27.8 percentile.
Root Cause
The root cause is missing authorization enforcement on credential-bearing configuration resources. The user_pass_show.cgi handler and its associated XML and JavaScript assets return credential fields to any authenticated caller, regardless of that caller's role. The design treats authentication as sufficient authorization, which violates the principle of least privilege and exposes secrets that should be restricted to administrators.
Attack Vector
Exploitation is network-based and requires only low-privilege authentication to the router's web interface. An attacker sends an HTTP request to user_pass_show.cgi or fetches ui_config_2.xml or misc.js from the management server. The response contains cleartext credential material that the attacker parses to obtain the administrator username and password. Full technical reproduction steps are documented in the GitHub User Pass Disclosure Report and the VulnCheck Advisory on Sensitive Data Exposure.
Detection Methods for CVE-2026-76859
Indicators of Compromise
- HTTP GET requests to /user_pass_show.cgi originating from non-administrative user sessions or unexpected internal hosts.
- Requests for ui_config_2.xml or misc.js from clients that do not correspond to normal management workstations.
- Successful administrator logins from source addresses that previously accessed user_pass_show.cgi under a low-privilege account.
Detection Strategies
- Inspect router access logs and upstream proxy logs for repeated retrieval of the affected CGI and configuration files.
- Correlate low-privilege authentication events with subsequent administrator logins from the same client address.
- Baseline normal management-plane traffic and alert on lateral requests to user_pass_show.cgi from user network segments.
Monitoring Recommendations
- Forward router web interface logs to a centralized SIEM for retention and correlation.
- Enable alerting on any HTTP 200 responses from user_pass_show.cgi where the requesting session role is not administrator.
- Review outbound connections from the router for signs of configuration exfiltration or unauthorized rule changes.
How to Mitigate CVE-2026-76859
Immediate Actions Required
- Restrict access to the router web management interface to trusted administrative networks only.
- Rotate all local router credentials, including the administrator password, after confirming no active low-privilege accounts exist on the device.
- Disable or remove low-privilege user accounts that are not strictly required for operations.
- Block external access to the management interface at the perimeter firewall.
Patch Information
No vendor patch is referenced in the current NVD entry for CVE-2026-76859. Administrators should monitor Netcore for firmware updates addressing user_pass_show.cgi and apply them immediately once available. Consult the VulnCheck Advisory on Sensitive Data Exposure for the latest remediation guidance.
Workarounds
- Place the router management interface behind an access control list that permits only known administrator IP addresses.
- Segment the router management VLAN from general user networks to prevent low-privilege users from reaching user_pass_show.cgi.
- Where feasible, replace the affected NR255-V firmware version 1.5.130703 with an unaffected device or firmware branch until a fix is released.
# Configuration example: restrict router management interface access
# Example iptables rule on an upstream gateway allowing only a trusted admin subnet
iptables -A FORWARD -p tcp -d 192.0.2.1 --dport 80 -s 10.10.0.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d 192.0.2.1 --dport 80 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.