VulnerabilityPublished 10 Jul 2025Updated 4 Aug 2025

CVE-2025-3947: Honeywell C300 PCNT02 · Integer Underflow

Affects Honeywell C300 PCNT02Source CVE Database V5

Not known to be exploited · CVSS 8.2 High.

Data as of 26 Oct 2026, 09:15 UTC

CVSS 3.1 base score

8.2High

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 30% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: High

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, 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: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
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 on the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 10 Jul 2025
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 26 Oct 2026.

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
Honeywell C300 PCNT02	Affected =520.1 =530	Fixed in–

AI-suggested

European organizations should prioritize immediate assessment of their Honeywell Experion PKS deployments to identify affected versions. Specific mitigation steps include: 1) Applying the vendor-recommended patches by upgrading to Honeywell Experion PKS versions 520.2 TCU9 HF1 or 530.1 TCU3 HF1 without delay. 2) Implement network segmentation to isolate control systems from general IT networks and limit exposure to untrusted networks. 3) Employ strict access controls and monitoring on the Control Data Access (CDA) interfaces to detect anomalous input data patterns that could indicate exploitation attempts. 4) Conduct thorough vulnerability scanning and penetration testing focused on industrial control system components to verify patch effectiveness and identify residual risks. 5) Implement intrusion detection systems (IDS) tailored for ICS environments to detect potential exploitation attempts in real time. 6) Develop and rehearse incident response plans specific to ICS denial of service scenarios to minimize operational impact. 7) Engage with Honeywell support and subscribe to threat intelligence feeds for updates on any emerging exploits or additional mitigations.

Description

The Honeywell Experion PKS contains an Integer Underflow vulnerability in the component Control Data Access (CDA). An attacker could potentially exploit this vulnerability, leading to Input Data Manipulation, which could result in improper integer data value checking during subtraction leading to a denial of service. Honeywell recommends updating to the most recent version of Honeywell Experion PKS:520.2 TCU9 HF1 and 530.1 TCU3 HF1. The affected Experion PKS products are C300 PCNT02, C300 PCNT05, FIM4, FIM8, UOC, CN100, HCA, C300PM, and C200E. The Experion PKS versions affected are from 520.1 through 520.2 TCU9 and from 530 through 530 TCU3.

Impact

For European organizations, especially those operating critical infrastructure such as energy, manufacturing, and utilities that rely on Honeywell Experion PKS for process control and automation, this vulnerability poses a significant risk. Exploitation could lead to denial of service, disrupting industrial processes and potentially causing safety hazards or production downtime. The lack of confidentiality impact reduces the risk of data leakage, but the integrity and availability impacts remain concerning. Given the network attack vector and no requirement for privileges or user interaction, remote exploitation is feasible, increasing the threat landscape. Disruption in critical infrastructure could have cascading effects on supply chains and essential services. Additionally, regulatory compliance frameworks in Europe, such as NIS2 Directive and GDPR, may impose strict requirements on managing such vulnerabilities and reporting incidents, increasing the operational and legal impact of exploitation.

References

process.honeywell.com (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 5 Aug 2025, 00:37 UTC

WeaknessesCWE-191

Technical details

References

Community reviews

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