CVE-2026-40854: CWE-290 Authentication bypass by spoofing in WNC T-Mobile 5G Box IDU
WNC T-Mobile 5G Box IDU router contains an authentication bypass vulnerability in the portal.cgi component. The session verification mechanism improperly validates the sessionid cookie by checking for the existence of a corresponding file in /tmp/login_user. An attacker can bypass authentication by using directory entries such as "." or ".." in the cookie, allowing unauthorized access to the administration panel.This issue has been fixed in firmware version 1.1.0.651412
AI Analysis
Technical Summary
CVE-2026-40854 is an authentication bypass vulnerability in the WNC T-Mobile 5G Box IDU router's portal.cgi component. The session verification mechanism improperly validates the sessionid cookie by merely checking for a corresponding file in /tmp/login_user. By exploiting directory traversal entries like "." or ".." in the sessionid cookie, an attacker can bypass authentication controls and gain unauthorized administrative access. This issue is resolved in firmware version 1.1.0.651412.
Potential Impact
Successful exploitation allows an attacker to bypass authentication and gain unauthorized access to the router's administration panel. This could lead to unauthorized configuration changes or control over the device. The CVSS 4.0 score is 8.7 (high severity), reflecting the ease of exploitation and significant impact on confidentiality, integrity, and availability.
Mitigation Recommendations
Upgrade the WNC T-Mobile 5G Box IDU router firmware to version 1.1.0.651412 or later, where this authentication bypass vulnerability has been fixed. No other mitigations are specified or required once the firmware is updated.
CVE-2026-40854: CWE-290 Authentication bypass by spoofing in WNC T-Mobile 5G Box IDU
Description
WNC T-Mobile 5G Box IDU router contains an authentication bypass vulnerability in the portal.cgi component. The session verification mechanism improperly validates the sessionid cookie by checking for the existence of a corresponding file in /tmp/login_user. An attacker can bypass authentication by using directory entries such as "." or ".." in the cookie, allowing unauthorized access to the administration panel.This issue has been fixed in firmware version 1.1.0.651412
CVSS v4.0
Score 8.7high
Affected software
WNC
T-Mobile 5G Box IDU
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-40854 is an authentication bypass vulnerability in the WNC T-Mobile 5G Box IDU router's portal.cgi component. The session verification mechanism improperly validates the sessionid cookie by merely checking for a corresponding file in /tmp/login_user. By exploiting directory traversal entries like "." or ".." in the sessionid cookie, an attacker can bypass authentication controls and gain unauthorized administrative access. This issue is resolved in firmware version 1.1.0.651412.
Potential Impact
Successful exploitation allows an attacker to bypass authentication and gain unauthorized access to the router's administration panel. This could lead to unauthorized configuration changes or control over the device. The CVSS 4.0 score is 8.7 (high severity), reflecting the ease of exploitation and significant impact on confidentiality, integrity, and availability.
Mitigation Recommendations
Upgrade the WNC T-Mobile 5G Box IDU router firmware to version 1.1.0.651412 or later, where this authentication bypass vulnerability has been fixed. No other mitigations are specified or required once the firmware is updated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- CERT-PL
- Date Reserved
- 2026-04-15T11:10:34.849Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6aaa7e3555bf5e2cf5884acb
Added to database: 09/16/2026, 11:32:05 UTC
Last enriched: 09/16/2026, 11:47:23 UTC
Last updated: 09/16/2026, 22:26:54 UTC
Views: 8
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