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VulnerabilityPublished

CVE-2026-53427: leandrocp mdex · Cross-site Scripting

Affects leandrocp mdexSource CVE Database V5

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Not known to be exploited · CVSS 2.3 Low : upgrade to 0.12.3 when convenient.

Data as of 10 Nov 2026, 23:24 UTC

CVSS 4.0 base score
2.3Low
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.6% chance of exploitation in 30 days – higher than 53% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 0.12.3, 6ed94d905f97af188323f042698ae841c02293b4, 0.2.3 +1
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 29 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 11 Nov 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
leandrocpmdexAffected
  • >=0.11.3 <0.12.3
Fixed in
  • 0.12.3
leandrocpmdexAffected
  • ≥ 0d7ffc84ea742e1daf666426814e5bb6d0499433, < 6ed94d905f97af188323f042698ae841c02293b4
Fixed in
  • 6ed94d905f97af188323f042698ae841c02293b4
leandrocpmdex_nativeAffected
  • >=0.1.0 <0.2.3
Fixed in
  • 0.2.3
leandrocpmdex_nativeAffected
  • ≥ 956528c5e31746253347029e810a969ab916fd27, < 798a363b4339f6f7162ec8437c4c9f9b5ae6fbf3
Fixed in
  • 798a363b4339f6f7162ec8437c4c9f9b5ae6fbf3
Hexmdexpkg:hex/mdexOther threatsAffected
  • >=0.11.3 <0.12.3
Fixed in
  • 0.12.3
Hexmdex_nativepkg:hex/mdex_nativeOther threatsAffected
  • >=0.1.0 <0.2.3
Fixed in
  • 0.2.3

CPE configurations (2)

  • cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*
  • cpe:2.3:a:leandrocp:mdex_native:*:*:*:*:*:*:*:*

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, avoid enabling syntax highlighting with full info-string forwarding (render: [full_info_string: true]) in affected versions. Restrict or sanitize user-submitted Markdown content to prevent injection of malicious info-string attributes.

Description

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 <div>. A single-quoted shell token preserves an inner double quote through shlex parsing, so a value such as '"><script>alert(1)</script>' 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.

References

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