PT-2026-53680 · Leandrocp · Mdex+1

Leandro Pereira + 1 · Published 2026-06-29 · Updated 2026-06-29 · CVE-2026-53427

NVD

CVSS v4.0

2.3

Low

Base vector

AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/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

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in leandrocp MDEx allows stored or reflected cross-site scripting via attacker-controlled Markdown.

When syntax highlighting and full info-string forwarding (render: [full info string: true]) are enabled, the Lumis adapter copies the value of a code fence's highlight lines class info-string attribute, unescaped, into the class attribute of every rendered line. comrak nif::lumis adapter::LumisAdapter::parse custom attributes in native/comrak nif/src/lumis adapter.rs shlex-parses the info string and stores each key=value pair verbatim, highlight lines config pulls highlight lines class into the per-line class value, and write highlighted interpolates that value directly into the class attribute of the per-line

. A single-quoted shell token preserves an inner double quote through shlex parsing, so a value such as '">' terminates the class attribute early and the markup that follows is emitted as live HTML.

An attacker who can submit Markdown (through comments, posts, wiki pages, documentation, or any user-generated content) can inject arbitrary HTML and JavaScript that runs in the browser of every user who views the rendered output, enabling session theft, account takeover, and other client-side attacks. No authentication or special privileges are required.

The vulnerable native code originally shipped inside mdex (in native/comrak nif/src/lumis adapter.rs) and was later extracted into the separate mdex native package (native/mdex native nif/src/lumis adapter.rs), where it remains unpatched.

This issue affects mdex from 0.11.3 before 0.12.3, and mdex native from 0.1.0 before 0.2.3.

Fix

XSS

Weakness Enumeration

CWE-79

Related Identifiers

CVE-2026-53427

Affected Products

Mdex

Mdex Native

References · 5

• https://github.com/leandrocp/mdex_native/security/advisories/GHSA-v664-pmxr-mxxx · Vendor Advisory
• https://github.com/leandrocp/mdex_native/commit/798a363b4339f6f7162ec8437c4c9f9b5ae6fbf3 · Patch
• https://nvd.nist.gov/vuln/detail/CVE-2026-53427 · Security Note
• https://osv.dev/vulnerability/EEF-CVE-2026-53427 · Note
• https://cna.erlef.org/cves/CVE-2026-53427.html · Note