CVE-2026-35556

High

Published: 09 April 2026

Published

09 April 2026

Modified

16 April 2026

KEV Added

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Patch

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CVSS Score 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS Score 0.0004 11.1th percentile

Risk Priority 15 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-35556 is a high-severity Plaintext Storage of a Password (CWE-256) vulnerability in Openplcproject Openplc V3 Firmware. Its CVSS base score is 7.5 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Unsecured Credentials (T1552); ranked at the 11.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 IA-5 (Authenticator Management) and SC-28 (Protection of Information at Rest).

Threat & Defense at a Glance

What attackers do: exploitation maps to Unsecured Credentials (T1552). What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SC-28 Protection of Information at Rest good match

prevent

Requires cryptographic mechanisms to protect confidentiality of sensitive information at rest, directly preventing retrieval of plaintext-stored passwords.

IA-5 Authenticator Management good match

prevent

Mandates protection of authenticators like passwords during storage commensurate with the sensitivity of protected information.

SI-2 Flaw Remediation good match

prevent

Requires timely identification, reporting, and correction of flaws such as plaintext password storage in this specific CVE.

MITRE ATT&CK Enterprise TechniquesAI

T1552 Unsecured Credentials Credential Access

Adversaries may search compromised systems to find and obtain insecurely stored credentials.

attack.mitre.org →

Why these techniques?

The vulnerability is explicitly plaintext storage of passwords (CWE-256), directly enabling retrieval of unsecured credentials as described in T1552 Unsecured Credentials.

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

OpenPLC_V3 is vulnerable to a Plaintext Storage of a Password vulnerability that could allow an attacker to retrieve credentials and access sensitive information.

Deeper analysisAI

CVE-2026-35556 is a Plaintext Storage of a Password vulnerability (CWE-256) in OpenPLC_V3, published on 2026-04-09. The issue enables attackers to retrieve credentials stored in plaintext, potentially granting access to sensitive information. It carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N), indicating high confidentiality impact with network accessibility and low attack complexity.

An unauthenticated attacker (PR:N) can exploit this vulnerability remotely over the network (AV:N) without requiring user interaction (UI:N). Exploitation involves accessing the affected component to extract plaintext credentials, allowing unauthorized disclosure of sensitive information (C:H) while leaving integrity and availability unaffected.

The CISA ICS Advisory ICSA-25-345-10 provides further details on this vulnerability, including potential mitigation steps, at https://www.cisa.gov/news-events/ics-advisories/icsa-25-345-10.