Is CVE-2026-39426 actively exploited?

No active exploitation of CVE-2026-39426 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-39426 be exploited remotely?

Yes. CVE-2026-39426 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-39426?

CVE-2026-39426 has a CVSS score of 5.4 (MEDIUM).

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MEDIUM

CVE-2026-39426

CWE-79Published: April 14, 2026· Updated: Apr 20, 2026

5.4

CVSS v3.1

EPSS:0.05%probability of exploitation in 30 daysPercentile:14.2th

Official Description

MaxKB is an open-source AI assistant for enterprise. Versions 2.7.1 and below contain a Stored Cross-Site Scripting (XSS) vulnerability where the frontend's MdRenderer.vue component parses custom <iframe_render> tags from LLM responses or Application Prologue configurations, bypassing standard Markdown sanitization and XSS filtering. The unsanitized HTML content is passed to the IframeRender.vue component, which renders it directly into an <iframe> via the srcdoc attribute configured with sandbox="allow-scripts allow-same-origin". This can be a dangerous combination, allowing injected scripts to escape the iframe and execute JavaScript in the parent window using window.parent. Since the Prologue is rendered for any user visiting an application's chat interface, this results in a high-impact Stored XSS that can lead to session hijacking, unauthorized actions, and sensitive data exposure. This issue has been fixed in version 2.8.0.

NVD Source

Technical Analysis

CVE-2026-39426 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.

From a weakness classification perspective (CWE-79): Cross-site scripting (XSS) vulnerabilities allow attackers to inject malicious scripts into web pages viewed by other users.