Is there a patch available for CVE-2026-39426?

Yes, a patch is available for CVE-2026-39426. Update the affected software to the latest version immediately.

Maxkb CVE-2026-39426

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

CVE-2026-39426 has a CVSS 4.0 base score of 5.1 (Medium). CVSS vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. EPSS exploitation probability: 0.0%.

EUVD-2026-22193 MEDIUM

Cross-site Scripting (XSS) (CWE-79)

2026-04-14 GitHub_M

XSS Information Disclosure Maxkb 1Panel Dev

5.1

CVSS 4.0 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

5.1 MEDIUM

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Scope

Lifecycle Timeline

Patch released

Apr 20, 2026 - 17:31 nvd

Patch available

Apr 16, 2026 - 05:29 EUVD

2.8.0

Analysis Generated

Apr 14, 2026 - 04:10 vuln.today

CVSS changed

Apr 14, 2026 - 02:22 NVD

5.1 (MEDIUM)

EUVD ID Assigned

Apr 14, 2026 - 02:00 euvd

EUVD-2026-22193

Analysis Generated

Apr 14, 2026 - 02:00 vuln.today

CVE Published

Apr 14, 2026 - 01:25 nvd

MEDIUM 5.1

DescriptionGitHub Advisory

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.

AnalysisAI

Stored Cross-Site Scripting in MaxKB's MdRenderer component allows authenticated users to inject malicious scripts via custom <iframe_render> tags in LLM responses or Application Prologue configurations, leading to JavaScript execution in the parent window context with access to session tokens and sensitive data. MaxKB versions 2.7.1 and earlier are affected; the vulnerability is fixed in version 2.8.0. The attack requires user interaction (UI:P) but impacts all visitors to an affected application's chat interface, making it a high-impact stored XSS despite the moderate CVSS 5.1 score.

Technical ContextAI

MaxKB's frontend rendering pipeline uses the MdRenderer.vue component to parse Markdown content from LLM responses and Application Prologue configurations. The component extracts and processes custom <iframe_render> tags without proper sanitization, then passes the unsanitized HTML to IframeRender.vue, which renders it directly into an <iframe> element using the srcdoc attribute. The iframe is configured with sandbox="allow-scripts allow-same-origin", which enables JavaScript execution while permitting cross-origin access within the same document. This combination allows injected scripts to use window.parent to escape sandbox isolation and execute arbitrary code in the parent window context, where they can access session storage, authentication tokens, and sensitive application data. The root cause is inadequate input validation (CWE-79: Improper Neutralization of Input During Web Page Generation) combined with unsafe iframe sandbox configuration.

RemediationAI

Vendor-released patch: MaxKB version 2.8.0 fixes the XSS vulnerability; upgrade all affected instances immediately. The patch removes or properly sanitizes custom <iframe_render> tag processing and hardens iframe sandbox configuration. Organizations unable to patch immediately should disable or restrict access to the Application Prologue feature and audit LLM response templates to prevent injection of custom tags. Monitor server logs for unusual <iframe_render> tag injection attempts. Apply the upgrade following your deployment process as documented in the MaxKB release notes at https://github.com/1Panel-dev/MaxKB/releases/tag/v2.8.0.