CVE-2026-40854 (GCVE-0-2026-40854)
Vulnerability from cvelistv5 – Published: 2026-09-16 11:21 – Updated: 2026-09-16 11:21
VLAI
EPSS
VEX
Title
Session auth bypass via cookie value in T-Mobile 5G Box IDU routers
Summary
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
Severity
CWE
- CWE-290 - Authentication bypass by spoofing
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://cert.pl/posts/2026/09/CVE-2026-40854 | third-party-advisory |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| WNC | T-Mobile 5G Box IDU |
Affected:
0 , < 1.1.0.651412
(custom)
cpe:2.3:a:wnc:t-mobile_5g_box_idu:*:*:*:*:*:*:*:* |
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"Recovery": "NOT_DEFINED",
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"description": "CWE-290 Authentication bypass by spoofing",
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"type": "CWE"
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"providerMetadata": {
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"orgId": "4bb8329e-dd38-46c1-aafb-9bf32bcb93c6",
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],
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}
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"source": {
"discovery": "EXTERNAL"
},
"title": "Session auth bypass via cookie value in T-Mobile 5G Box IDU routers",
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"cveId": "CVE-2026-40854",
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"dateReserved": "2026-04-15T11:10:34.849Z",
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"state": "PUBLISHED"
},
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"dataVersion": "5.2",
"vulnerability-lookup:meta": {
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}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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