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CVE-2026-40854 is an authentication-bypass vulnerability affecting WNC T-Mobile 5G Box IDU router firmware versions prior to 1.1.0.651412. Session validation improperly determines whether a supplied sessionid cookie is valid by testing for the existence of a corresponding filesystem object. Directory-entry values, including dot and dot-dot, can satisfy this check and bypass authentication.
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No public exploit code observed for this vulnerability.
3 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An authentication-bypass vulnerability in the portal.cgi component of WNC T-Mobile 5G Box IDU routers. Manipulated sessionid cookie values can provide unauthorized access to the administration panel.
An authentication-bypass flaw in the portal.cgi component of WNC T-Mobile 5G Box IDU routers. Improper validation of the sessionid cookie permits use of directory entries such as "." or ".." to bypass portal authentication and access the router administration panel.
A reported vulnerability in the firmware of WNC T-Mobile 5G Box IDU routers; no technical details are provided.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.