CVE-2026-4436

High

Published: 09 April 2026

Published

09 April 2026

Modified

13 April 2026

KEV Added

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Patch

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CVSS Score 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

EPSS Score 0.0006 19.6th percentile

Risk Priority 17 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-4436 is a high-severity Missing Authentication for Critical Function (CWE-306) vulnerability in Sharepoint (inferred from references). Its CVSS base score is 8.6 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 19.6th 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 AC-14 (Permitted Actions Without Identification or Authentication) and IA-9 (Service Identification and Authentication).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

AC-14 Permitted Actions Without Identification or Authentication good match

prevent

Directly addresses CWE-306 by prohibiting critical Modbus register manipulations for odorant injection without identification and authentication.

IA-9 Service Identification and Authentication good match

prevent

Requires the odorant injection service to authenticate remote Modbus clients before processing register value changes.

SC-7 Boundary Protection good match

prevent

Implements network segmentation and boundary protections to block unauthorized remote Modbus packets from reaching the vulnerable system.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1210 Exploitation of Remote Services Lateral Movement

Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.

attack.mitre.org →

Why these techniques?

Missing authentication for critical Modbus register manipulation enables remote unauthenticated exploitation of public-facing ICS applications and remote services to alter control logic.

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

NVD Description

A low-privileged remote attacker can send Modbus packets to manipulate register values that are inputs to the odorant injection logic such that too much or too little odorant is injected into a gas line.

Deeper analysisAI

CVE-2026-4436 is a vulnerability (CWE-306: Missing Authentication for Critical Function) in odorant injection logic within gas line systems that use Modbus protocol for register management. A low-privileged remote attacker can send Modbus packets to manipulate register values serving as inputs to this logic, resulting in excessive or insufficient odorant injection. The vulnerability carries a CVSS v3.1 base score of 8.6 (AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N) and was published on 2026-04-09. Affected components are outlined in CISA ICS Advisory ICSA-26-099-02, with details linked to Linc Energy Systems.

A network-accessible attacker requires no privileges or user interaction to exploit this issue remotely with low complexity. By crafting and transmitting Modbus packets, the attacker can arbitrarily alter critical register values, directly influencing the odorant injection process. This enables injection of too much or too little odorant into the gas line, potentially compromising gas detection safety mechanisms that rely on odorant for leak identification.

Advisories including CISA ICSA-26-099-02 (https://www.cisa.gov/news-events/ics-advisories/icsa-26-099-02), the associated CSAF JSON (https://github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2026/icsa-26-099-02.json), and Linc Energy Systems documentation (https://lincenergysystems-my.sharepoint.com/:f:/p/h_baer/IgDYaHIhXpyLQJvnKPd6b80TAUgV7Lp8qmVYBFUb0lmr7ak?e=JLeADm) provide mitigation guidance. Security practitioners should review these for vendor-recommended patches, configuration hardening, network segmentation, and Modbus access controls to prevent unauthorized packet injection.