CVE-2025-34256Public exploitNetwork attack vector

Unauthenticated account takeover via hard-coded JWT key

Published Dec 5, 2025 · Updated Aug 14, 2026

Hard-coded key use in Advantech WISE-DeviceOn Server before 5.4 allows remote attackers to impersonate any account with a forged JWT. AuthUtil builds the EIRMMToken HS512 signer and verifier from one static secret, then accepts the token when its email claim matches an account. Knowledge of a valid email is the only account-specific gate; impersonating the root super admin grants server control and command execution on managed agents.

CVSS severity10.0
Critical
EPSS probability0.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Hard-coded key use in Advantech WISE-DeviceOn Server before 5.4 allows remote attackers to impersonate any account with a forged JWT. AuthUtil builds the EIRMMToken HS512 signer and verifier from one static secret, then accepts the token when its email claim matches an account. Knowledge of a valid email is the only account-specific gate; impersonating the root super admin grants server control and command execution on managed agents.

The record

CVE
CVE-2025-34256
Published
Dec 5, 2025
Updated
Aug 14, 2026
Vendor
Advantech
Product
DeviceOn Server
Classifications
CWE-321, T1606.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 5, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <5.4.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Advantech · DeviceOn Serverversion=0 <5.4.0

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
10.0VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-321Use of Hard-coded Cryptographic Key
T1606.001Forge Web Credentials: Web Cookies

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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