CVE-2026-39426Network attack vector

Stored XSS via unsanitized iframe srcdoc

Published Apr 14, 2026 · Updated Apr 14, 2026

Stored XSS in MdRenderer.vue in MaxKB before 2.8.0 allows remote authenticated users to execute JavaScript when a user opens crafted chat content. MdRenderer.vue extracts iframe_render content before Markdown sanitization, and IframeRender.vue assigns that HTML to an iframe srcdoc with script and same-origin sandbox permissions. An attacker must control an LLM response or application prologue and wait for a user to visit the chat interface, enabling session access, data exposure, and actions with that user's authority.

CVSS severity5.1
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in MdRenderer.vue in MaxKB before 2.8.0 allows remote authenticated users to execute JavaScript when a user opens crafted chat content. MdRenderer.vue extracts iframe_render content before Markdown sanitization, and IframeRender.vue assigns that HTML to an iframe srcdoc with script and same-origin sandbox permissions. An attacker must control an LLM response or application prologue and wait for a user to visit the chat interface, enabling session access, data exposure, and actions with that user's authority.

The record

CVE
CVE-2026-39426
Published
Apr 14, 2026
Updated
Apr 14, 2026
Vendor
KubeOperator
Product
MaxKB
Classifications
CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.8.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

KubeOperator · MaxKBversion=< 2.8.0

Published CVSS scores

5.1GitHub, Inc.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
5.4National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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