CVE-2026-53427Public exploitNetwork attack vector

Cross-site scripting via unescaped line class

Published Jun 29, 2026 · Updated Jun 29, 2026

Cross-site scripting in MDEx 0.11.3 through 0.12.2 and MDExNative 0.1.0 through 0.2.2 allows remote attackers to inject script via Markdown. LumisAdapter shlex-parses highlight_lines_class verbatim, and write_highlighted interpolates it unescaped into each rendered line's double-quoted class attribute. Exposure requires untrusted Markdown, Lumis syntax highlighting, full_info_string enabled, and a viewer; injected JavaScript runs in that viewer's browser.

CVSS severity2.3
Low
EPSS probability0.69%
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 MDEx 0.11.3 through 0.12.2 and MDExNative 0.1.0 through 0.2.2 allows remote attackers to inject script via Markdown. LumisAdapter shlex-parses highlight_lines_class verbatim, and write_highlighted interpolates it unescaped into each rendered line's double-quoted class attribute. Exposure requires untrusted Markdown, Lumis syntax highlighting, full_info_string enabled, and a viewer; injected JavaScript runs in that viewer's browser.

The record

CVE
CVE-2026-53427
Published
Jun 29, 2026
Updated
Jun 29, 2026
Vendor
Leandro Pereira
Product
MDExNative
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 29, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 29, 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=0.1.0 <0.2.3
  2. Affected versionversion=956528c5e31746253347029e810a969ab916fd27 <798a363b4339f6f7162ec8437c4c9f9b5ae6fbf3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Leandro Pereira · MDExNativeversion=0.1.0 <0.2.3; version=956528c5e31746253347029e810a969ab916fd27 <798a363b4339f6f7162ec8437c4c9f9b5ae6fbf3
Leandro Pereira · MDExversion=0.11.3 <0.12.3; version=0d7ffc84ea742e1daf666426814e5bb6d0499433 <6ed94d905f97af188323f042698ae841c02293b4

Published CVSS scores

2.3EEFCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/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 exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007Command and Scripting Interpreter: JavaScript

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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