CVE-2026-54889
Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in leandrocp mdex allows cross-site scripting via unsanitized URL schemes in Quill Delta output.
'Elixir.MDEx':to_delta/2 converts Markdown into a Quill Delta. 'Elixir.MDEx.DeltaConverter':default_convert_node/3 in lib/mdex/delta_converter.ex copies the URL of a link, wikilink, or image node directly from the parsed Markdown into the Delta "link" or "image" attribute without applying a scheme allowlist or any normalization.
An attacker who controls the Markdown text can supply a javascript: URL (for example [click](javascript:alert(document.cookie))) that survives verbatim into the Delta attribute.
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When the Delta is rendered to HTML by a downstream renderer (such as quill-delta-to-html or the Quill client), the attribute becomes an <a href> or <img src>, and the javascript: scheme executes in the browser of anyone who views the rendered content. The link and wikilink cases are the strongest vectors because javascript: in an href executes on click; the image case is lower impact because javascript: in <img src> generally does not execute in modern browsers.
This issue affects mdex: from 0.8.3 before 0.13.2.
CVSS
- Versión: 4.0
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/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
- Puntuación base: 5.1
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.54%
- Percentil entre todas las CVEs puntuadas: 43
- Fecha de la puntuación: 2/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
CWE
- CWE-79
Referencias
- https://cna.erlef.org/cves/CVE-2026-54889.html
- https://github.com/leandrocp/mdex/commit/2817147f5b87ce7186aa604c9ee72499485b8f2f
- https://github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph
- https://osv.dev/vulnerability/EEF-CVE-2026-54889
- https://github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph
JSON original (NVD)
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{
"id": "CVE-2026-54889",
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"metrics": {
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"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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"id": "CVE-2026-54889",
"role": "CISA Coordinator",
"options": [
{
"exploitation": "poc"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"version": "2.0.3",
"timestamp": "2026-06-29T20:48:34.044130Z"
}
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"type": "Secondary",
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"version": "4.0",
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"attackVector": "NETWORK",
"baseSeverity": "MEDIUM",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/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",
"exploitMaturity": "NOT_DEFINED",
"providerUrgency": "NOT_DEFINED",
"userInteraction": "ACTIVE",
"attackComplexity": "LOW",
"attackRequirements": "NONE",
"privilegesRequired": "NONE",
"subIntegrityImpact": "LOW",
"vulnIntegrityImpact": "LOW",
"integrityRequirement": "NOT_DEFINED",
"modifiedAttackVector": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"vulnAvailabilityImpact": "NONE",
"availabilityRequirement": "NOT_DEFINED",
"modifiedUserInteraction": "NOT_DEFINED",
"modifiedAttackComplexity": "NOT_DEFINED",
"subConfidentialityImpact": "LOW",
"vulnConfidentialityImpact": "LOW",
"confidentialityRequirement": "NOT_DEFINED",
"modifiedAttackRequirements": "NOT_DEFINED",
"modifiedPrivilegesRequired": "NOT_DEFINED",
"modifiedSubIntegrityImpact": "NOT_DEFINED",
"modifiedVulnIntegrityImpact": "NOT_DEFINED",
"vulnerabilityResponseEffort": "NOT_DEFINED",
"modifiedSubAvailabilityImpact": "NOT_DEFINED",
"modifiedVulnAvailabilityImpact": "NOT_DEFINED",
"modifiedSubConfidentialityImpact": "NOT_DEFINED",
"modifiedVulnConfidentialityImpact": "NOT_DEFINED"
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"affected": [
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"affectedData": [
{
"cpes": [
"cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*"
],
"repo": "https://github.com/leandrocp/mdex",
"vendor": "leandrocp",
"modules": [
"'Elixir.MDEx'",
"'Elixir.MDEx.DeltaConverter'"
],
"product": "mdex",
"versions": [
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"version": "0.8.3",
"lessThan": "0.13.2",
"versionType": "semver"
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"packageURL": "pkg:hex/mdex",
"packageName": "mdex",
"programFiles": [
"lib/mdex.ex",
"lib/mdex/delta_converter.ex"
],
"collectionURL": "https://repo.hex.pm",
"defaultStatus": "unaffected",
"programRoutines": [
{
"name": "'Elixir.MDEx':to_delta/2"
},
{
"name": "'Elixir.MDEx.DeltaConverter':convert/2"
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{
"name": "'Elixir.MDEx.DeltaConverter':default_convert_node/3"
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},
{
"cpes": [
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],
"repo": "https://github.com/leandrocp/mdex",
"vendor": "leandrocp",
"modules": [
"'Elixir.MDEx'",
"'Elixir.MDEx.DeltaConverter'"
],
"product": "mdex",
"versions": [
{
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"version": "9852db2456fdc9d856eb636603a7f608e22e3793",
"lessThan": "2817147f5b87ce7186aa604c9ee72499485b8f2f",
"versionType": "git"
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],
"packageURL": "pkg:github/leandrocp/mdex",
"packageName": "leandrocp/mdex",
"programFiles": [
"lib/mdex.ex",
"lib/mdex/delta_converter.ex"
],
"collectionURL": "https://github.com",
"defaultStatus": "unaffected",
"programRoutines": [
{
"name": "'Elixir.MDEx':to_delta/2"
},
{
"name": "'Elixir.MDEx.DeltaConverter':convert/2"
},
{
"name": "'Elixir.MDEx.DeltaConverter':default_convert_node/3"
}
]
}
]
}
],
"published": "2026-06-29T20:17:39.407",
"references": [
{
"url": "https://cna.erlef.org/cves/CVE-2026-54889.html",
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
},
{
"url": "https://github.com/leandrocp/mdex/commit/2817147f5b87ce7186aa604c9ee72499485b8f2f",
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
},
{
"url": "https://github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph",
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
},
{
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-54889",
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
},
{
"url": "https://github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph",
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
}
],
"vulnStatus": "Deferred",
"weaknesses": [
{
"type": "Secondary",
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"description": [
{
"lang": "en",
"value": "CWE-79"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in leandrocp mdex allows cross-site scripting via unsanitized URL schemes in Quill Delta output.\n\n'Elixir.MDEx':to_delta/2 converts Markdown into a Quill Delta. 'Elixir.MDEx.DeltaConverter':default_convert_node/3 in lib/mdex/delta_converter.ex copies the URL of a link, wikilink, or image node directly from the parsed Markdown into the Delta \"link\" or \"image\" attribute without applying a scheme allowlist or any normalization.\n\nAn attacker who controls the Markdown text can supply a javascript: URL (for example [click](javascript:alert(document.cookie))) that survives verbatim into the Delta attribute. When the Delta is rendered to HTML by a downstream renderer (such as quill-delta-to-html or the Quill client), the attribute becomes an <a href> or <img src>, and the javascript: scheme executes in the browser of anyone who views the rendered content. The link and wikilink cases are the strongest vectors because javascript: in an href executes on click; the image case is lower impact because javascript: in <img src> generally does not execute in modern browsers.\n\nThis issue affects mdex: from 0.8.3 before 0.13.2."
}
],
"lastModified": "2026-06-30T14:14:35.520",
"sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
}