CVE-2026-3071

High

Published: 26 February 2026

Published

26 February 2026

Modified

15 April 2026

KEV Added

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Patch

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CVSS Score 8.4 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Score 0.0008 24.1th percentile

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

Summary

CVE-2026-3071 is a high-severity Deserialization of Untrusted Data (CWE-502) vulnerability in Hiddenlayer (inferred from references). Its CVSS base score is 8.4 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked at the 24.1th 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 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploitation for Client Execution (T1203) 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

SI-2 Flaw Remediation good match

prevent

Remediates the deserialization vulnerability in Flair's LanguageModel class by applying vendor patches, directly preventing arbitrary code execution from malicious models.

SI-10 Information Input Validation good match

prevent

Requires validation of untrusted model files prior to deserialization in the LanguageModel class, blocking malicious data that could lead to code execution.

SI-7 Software, Firmware, and Information Integrity good match

preventdetect

Enforces integrity verification of software and model files loaded by Flair, detecting and preventing execution of tampered or malicious deserialized content.

MITRE ATT&CK Enterprise TechniquesAI

T1203 Exploitation for Client Execution Execution

Adversaries may exploit software vulnerabilities in client applications to execute code.

attack.mitre.org →

T1059.006 Python Execution

Adversaries may abuse Python commands and scripts for execution.

attack.mitre.org →

Why these techniques?

Deserialization of untrusted model data directly enables arbitrary code execution in a Python library (Flair), mapping to client-side exploitation (T1203) and Python interpreter abuse (T1059.006) with local attack vector and no UI required.

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

NVD Description

Deserialization of untrusted data in the LanguageModel class of Flair from versions 0.4.1 to latest are vulnerable to arbitrary code execution when loading a malicious model.

Deeper analysisAI

CVE-2026-3071 is a deserialization of untrusted data vulnerability (CWE-502) in the LanguageModel class of the Flair library, affecting versions 0.4.1 through the latest release. Published on 2026-02-26, it enables arbitrary code execution when an application loads a malicious model using the affected class. The issue carries a CVSS v3.1 base score of 8.4 (AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating high severity due to its potential for significant impact.

A local attacker can exploit this vulnerability with low complexity, requiring no privileges or user interaction. By supplying a malicious model file, the attacker tricks the Flair-based application into deserializing untrusted data during model loading, resulting in arbitrary code execution on the host system with the privileges of the running process. This could lead to full system compromise if the application processes untrusted models.

Advisories detailing mitigations and patches are available from HiddenLayer at https://www.hiddenlayer.com/sai-security-advisory/2026-02-flair.