CVE-2026-6827Network attack vector

Cross-site scripting via sanitizer and serialization bypasses

Published Aug 23, 2026 · Updated Aug 23, 2026

Cross-site scripting in Emil Stenström JustHTML before 1.17.0 allows remote attackers to inject active HTML through crafted content. Foreign-namespace, style, and programmatic DOM paths preserve or serialize browser-active markup instead of neutralizing it before reparse. Exploitation requires non-default SVG, MathML, or style policies, or DOM mutation followed by browser rendering; crafted cycles can instead hang DOM operations.

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

Cross-site scripting in Emil Stenström JustHTML before 1.17.0 allows remote attackers to inject active HTML through crafted content. Foreign-namespace, style, and programmatic DOM paths preserve or serialize browser-active markup instead of neutralizing it before reparse. Exploitation requires non-default SVG, MathML, or style policies, or DOM mutation followed by browser rendering; crafted cycles can instead hang DOM operations.

The record

CVE
CVE-2026-6827
Published
Aug 23, 2026
Updated
Aug 23, 2026
Vendor
Emil Stenström
Product
JustHTML
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 23, 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=0 <1.16.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Emil Stenström · JustHTMLversion=0 <1.16.0

Published CVSS scores

5.1National Vulnerability DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA: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
Privilegesunauthenticated
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.

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Technologies

Your stack

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Your stack

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