CVE-2025-66598VulnerabilityPublished 9 Feb 2026

CVE-2025-66598: Yokogawa Electric FAST/TOOLS · Weak Cryptography

Affects Yokogawa Electric FAST/TOOLSSource CVE Database V5

Not known to be exploited · CVSS 7.1 High.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 4.0 base score

7.1High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
Vulnerable system confidentiality: High
Vulnerable system integrity: Low
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: High: There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 9 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Yokogawa Electric CorporationFAST/TOOLS	Affected ≥ R9.01, ≤ R10.04	Fixed in–

AI-suggested

1. Immediately disable support for legacy SSL/TLS protocols (e.g., SSL 2.0, SSL 3.0, TLS 1.0, TLS 1.1) on FAST/TOOLS web servers and related infrastructure to prevent use of weak cryptographic algorithms. 2. Monitor Yokogawa Electric Corporation's advisories closely and apply official patches or updates as soon as they become available. 3. Implement network segmentation and strict firewall rules to limit access to FAST/TOOLS management interfaces to trusted internal networks only. 4. Deploy intrusion detection/prevention systems (IDS/IPS) capable of detecting anomalous SSL/TLS traffic or attempts to exploit weak cryptographic protocols. 5. Conduct regular cryptographic audits and vulnerability assessments on industrial control systems to identify and remediate weak encryption usage. 6. Utilize VPNs or other secure tunneling mechanisms for remote access to FAST/TOOLS to add an additional layer of encryption and authentication. 7. Train operational technology (OT) security teams on the risks of legacy cryptographic protocols and ensure incident response plans include scenarios involving cryptographic vulnerabilities. 8. Review and update cryptographic policies to mandate the use of modern, secure TLS versions (TLS 1.2 or higher) and strong cipher suites across all industrial communication channels.

Description

CVE-2025-66598 is a high-severity vulnerability in Yokogawa Electric Corporation's FAST/TOOLS software versions R9.01 to R10.04. The issue arises from the product's support for outdated SSL/TLS protocols, which use broken or risky cryptographic algorithms (CWE-327). This flaw potentially allows attackers to decrypt communications between clients and the web server, compromising confidentiality. The vulnerability requires no user interaction and can be exploited remotely without authentication, increasing its risk. Although no known exploits are currently active in the wild, the vulnerability's presence in critical industrial control system software raises significant concerns. European organizations using FAST/TOOLS in sectors like energy, manufacturing, and utilities are at risk. Mitigation involves disabling legacy SSL/TLS versions, applying vendor patches once available, and implementing network-level protections. Countries with substantial industrial automation deployments, such as Germany, France, Italy, and the UK, are most likely to be affected.

Impact

The primary impact of CVE-2025-66598 on European organizations lies in the potential compromise of confidentiality for communications within industrial control systems using FAST/TOOLS. Attackers could decrypt sensitive operational data, including process control commands and monitoring information, which may lead to industrial espionage, operational disruption, or preparation for more advanced attacks. While integrity and availability impacts are lower, the exposure of confidential data can undermine trust and compliance with data protection regulations such as GDPR. European critical infrastructure sectors—energy, manufacturing, utilities—relying on Yokogawa's software are particularly vulnerable. The ability to exploit this vulnerability remotely without authentication increases the attack surface. If exploited, it could facilitate further attacks, including man-in-the-middle (MitM) or replay attacks, potentially disrupting industrial processes. The lack of known exploits in the wild currently reduces immediate risk but does not diminish the urgency for mitigation given the high-value targets involved.

Summary

CVE-2025-66598 identifies a cryptographic vulnerability in Yokogawa Electric Corporation's FAST/TOOLS software suite, specifically versions R9.01 through R10.04. The root cause is the continued support for outdated SSL/TLS protocols that rely on weak or broken cryptographic algorithms, categorized under CWE-327. These legacy protocols are susceptible to cryptanalysis attacks that can decrypt intercepted communications, thereby exposing sensitive data transmitted between clients and the FAST/TOOLS web server interface. The vulnerability is remotely exploitable without requiring authentication or user interaction, which significantly lowers the barrier for attackers. FAST/TOOLS is widely used in industrial control systems (ICS) for monitoring and managing critical infrastructure, making the confidentiality breach particularly impactful. The CVSS v4.0 score of 7.1 reflects a high severity, emphasizing the potential for significant data exposure (high confidentiality impact), moderate integrity impact, and low availability impact. No public exploits have been reported yet, but the risk remains elevated due to the critical nature of the affected systems. The lack of available patches at the time of publication necessitates immediate interim mitigations such as disabling legacy SSL/TLS support and enhancing network security controls. This vulnerability underscores the importance of modern cryptographic standards in industrial environments to prevent interception and decryption of sensitive operational data.

CWE-327Use of a Broken or Risky Cryptographic Algorithm (opens in a new tab)
Class weaknessLikelihood of exploit: HighOWASP Top 10 A04:2025: Cryptographic Failures (opens in a new tab)
The product uses a broken or risky cryptographic algorithm or protocol.
Architecture and Design · Libraries or Frameworks
When there is a need to store or transmit sensitive data, use strong, up-to-date cryptographic algorithms to encrypt that data. Select a well-vetted algorithm that is currently considered to be strong by experts in the field, and use well-tested implementations.
Architecture and Design
Ensure that the design allows one cryptographic algorithm to be replaced with another in the next generation or version. Where possible, use wrappers to make the interfaces uniform. This will make it easier to upgrade to stronger algorithms.
Architecture and Design
Carefully manage and protect cryptographic keys (see CWE-320). If the keys can be guessed or stolen, then the strength of the cryptography itself is irrelevant.
OWASP Cheat Sheets
Cryptographic Storage (opens in a new tab)
Key Management (opens in a new tab)
Transport Layer Protection (opens in a new tab)
User Privacy Protection (opens in a new tab)
Password Storage (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.7 (opens in a new tab)
V2.9.3 (opens in a new tab)
V6.2.2 (opens in a new tab)
Attack patterns
Encryption Brute Forcing (opens in a new tab)
Creating a Rogue Certification Authority Certificate (opens in a new tab)
Signature Spoof (opens in a new tab)
Signature Spoofing by Improper Validation (opens in a new tab)
Cryptanalysis of Cellular Encryption (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

web-material3.yokogawa.com/1/39206/files/YSAR-26-0001-E.pdf (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 16 Feb 2026, 13:19 UTC

WeaknessesCWE-327

Technical details

References

Community reviews

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