Session auth bypass via cookie value in T-Mobile 5G Box IDU routers
Historical advisory recorded 23 Oct 2026 15:48:27 UTC. Read the latest advisory.
cve-program · CVE-2026-40854
PublishedWNC 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
Read the publisher's advisoryAffected versions, risk and source history
cve-program · CVE-2026-40854
PublishedSession auth bypass via cookie value in T-Mobile 5G Box IDU routers
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
- Source published
- 16 Sep 2026 11:21:10 UTC
- Source modified
- 16 Sep 2026 17:41:03 UTC
- Saved here
- 23 Oct 2026 15:48:27 UTC
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CVSS 4.0 · 8.7 CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N