CVE-2026-86644Public exploitNetwork attack vector

Stored XSS via unsanitized Mermaid SVG rendering

Published Sep 8, 2026 · Updated Sep 8, 2026

Stored XSS in ShowDoc 3.9.0 through 3.9.1 allows remote authenticated users to execute script when another user views a saved page. The Mermaid path in web_src/public/editor.md/editormd.js inserts generated SVG without DOMPurify sanitization and uses permissive label settings. An account able to edit a page must store the payload, and a victim must open the page; execution occurs in the victim's browser context.

CVSS severity3.5
Low
EPSS probability0.34%
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 ShowDoc 3.9.0 through 3.9.1 allows remote authenticated users to execute script when another user views a saved page. The Mermaid path in web_src/public/editor.md/editormd.js inserts generated SVG without DOMPurify sanitization and uses permissive label settings. An account able to edit a page must store the payload, and a victim must open the page; execution occurs in the victim's browser context.

The record

CVE
CVE-2026-86644
Published
Sep 8, 2026
Updated
Sep 8, 2026
Vendor
ShowDoc
Product
ShowDoc
Classifications
CWE-79, CWE-94, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 8, 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=3.9.0
  2. Affected versionversion=3.9.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

ShowDoc · ShowDocversion=3.9.0; version=3.9.1

Published CVSS scores

5.1VulDB CNACVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
3.5VulDB CNACVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
4.0VulDB CNAAV:N/AC:L/Au:S/C:N/I:P/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 exploitPublished

Weakness, pattern, technique

CWE-79Cross Site Scripting
CWE-94Code Injection
T1203Exploitation for Client Execution

Public exploit references

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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