CVE-2026-53428 (GCVE-0-2026-53428)
Vulnerability from cvelistv5 – Published: 2026-06-29 18:52 – Updated: 2026-06-30 04:38
VLAI
EPSS
VEX
Title
Unbounded memory allocation in highlight_lines range expansion in mdex
Summary
Memory Allocation with Excessive Size Value vulnerability in leandrocp mdex allows an unauthenticated attacker to cause a denial of service through unbounded memory allocation.
comrak_nif::lumis_adapter::LumisAdapter::parse_highlight_lines in native/comrak_nif/src/lumis_adapter.rs eagerly expands a user-controlled inclusive line range from a fenced code block's highlight_lines decorator into a Vec<usize>, pushing one element per integer in the range with no upper bound on the range size. An attacker who can supply Markdown that an application renders with MDEx.to_html/2 (for example a comment, chat message, or wiki page) can embed a code block whose info string is rust highlight_lines="1-100000000", forcing the native adapter to allocate roughly 8 bytes per line in the range.
A payload that differs by only a few bytes can therefore allocate hundreds of megabytes, and a sufficiently large range (for example 1-2000000000) exhausts host memory and aborts the BEAM, denying service to every user of the rendering process. The per-line write loop additionally tests membership with a linear scan over the same vector, degrading rendering to a quadratic cost even for ranges that do not immediately exhaust memory.
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 0.11.0 before 0.12.3, and mdex_native from 0.1.0 before 0.2.3.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-29 19:17 UTC
CWE
- CWE-789 - Memory Allocation with Excessive Size Value
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/leandrocp/mdex_native/security… | vendor-advisoryrelated |
| https://cna.erlef.org/cves/CVE-2026-53428.html | related |
| https://osv.dev/vulnerability/EEF-CVE-2026-53428 | related |
| https://github.com/leandrocp/mdex_native/commit/7… | patch |
Impacted products
4 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| leandrocp | mdex |
Affected:
0.11.0 , < 0.12.3
(semver)
cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:* |
||
| leandrocp | mdex |
Affected:
a8407611715d1ead35fbcba79c72cef1b7df387b , < 6ed94d905f97af188323f042698ae841c02293b4
(git)
cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:* |
||
| leandrocp | mdex_native |
Affected:
0.1.0 , < 0.2.3
(semver)
cpe:2.3:a:leandrocp:mdex_native:*:*:*:*:*:*:*:* |
||
| leandrocp | mdex_native |
Affected:
956528c5e31746253347029e810a969ab916fd27 , < 798a363b4339f6f7162ec8437c4c9f9b5ae6fbf3
(git)
cpe:2.3:a:leandrocp:mdex_native:*:*:*:*:*:*:*:* |
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"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "LOCAL",
"availabilityRequirement": "NOT_DEFINED",
"baseScore": 6.9,
"baseSeverity": "MEDIUM",
"confidentialityRequirement": "NOT_DEFINED",
"exploitMaturity": "NOT_DEFINED",
"integrityRequirement": "NOT_DEFINED",
"modifiedAttackComplexity": "NOT_DEFINED",
"modifiedAttackRequirements": "NOT_DEFINED",
"modifiedAttackVector": "NOT_DEFINED",
"modifiedPrivilegesRequired": "NOT_DEFINED",
"modifiedSubAvailabilityImpact": "NOT_DEFINED",
"modifiedSubConfidentialityImpact": "NOT_DEFINED",
"modifiedSubIntegrityImpact": "NOT_DEFINED",
"modifiedUserInteraction": "NOT_DEFINED",
"modifiedVulnAvailabilityImpact": "NOT_DEFINED",
"modifiedVulnConfidentialityImpact": "NOT_DEFINED",
"modifiedVulnIntegrityImpact": "NOT_DEFINED",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "HIGH",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/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",
"version": "4.0",
"vulnAvailabilityImpact": "HIGH",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-53428",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-06-29T19:17:11.005816Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-06-29T19:16:41.817",
"references": [
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://cna.erlef.org/cves/CVE-2026-53428.html"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/leandrocp/mdex_native/commit/798a363b4339f6f7162ec8437c4c9f9b5ae6fbf3"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/leandrocp/mdex_native/security/advisories/GHSA-j93q-9cvj-rxfm"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-53428"
}
],
"sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"vulnStatus": "Deferred",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-789"
}
],
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"type": "Secondary"
}
]
}
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-53428",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-06-29T19:17:11.005816Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-06-29T19:17:17.976Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://repo.hex.pm",
"cpes": [
"cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.MDEx\u0027",
"comrak_nif"
],
"packageName": "mdex",
"packageURL": "pkg:hex/mdex",
"product": "mdex",
"programFiles": [
"native/comrak_nif/src/lumis_adapter.rs"
],
"programRoutines": [
{
"name": "comrak_nif::lumis_adapter::LumisAdapter::parse_highlight_lines"
},
{
"name": "\u0027Elixir.MDEx\u0027:to_html/2"
}
],
"repo": "https://github.com/leandrocp/mdex",
"vendor": "leandrocp",
"versions": [
{
"lessThan": "0.12.3",
"status": "affected",
"version": "0.11.0",
"versionType": "semver"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.MDEx\u0027",
"comrak_nif"
],
"packageName": "leandrocp/mdex",
"packageURL": "pkg:github/leandrocp/mdex",
"product": "mdex",
"programFiles": [
"native/comrak_nif/src/lumis_adapter.rs"
],
"programRoutines": [
{
"name": "comrak_nif::lumis_adapter::LumisAdapter::parse_highlight_lines"
},
{
"name": "\u0027Elixir.MDEx\u0027:to_html/2"
}
],
"repo": "https://github.com/leandrocp/mdex",
"vendor": "leandrocp",
"versions": [
{
"lessThan": "6ed94d905f97af188323f042698ae841c02293b4",
"status": "affected",
"version": "a8407611715d1ead35fbcba79c72cef1b7df387b",
"versionType": "git"
}
]
},
{
"collectionURL": "https://repo.hex.pm",
"cpes": [
"cpe:2.3:a:leandrocp:mdex_native:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.MDExNative.Comrak\u0027",
"mdex_native_nif"
],
"packageName": "mdex_native",
"packageURL": "pkg:hex/mdex_native",
"product": "mdex_native",
"programFiles": [
"native/mdex_native_nif/src/lumis_adapter.rs"
],
"programRoutines": [
{
"name": "mdex_native_nif::lumis_adapter::LumisAdapter::parse_highlight_lines"
},
{
"name": "\u0027Elixir.MDExNative.Native\u0027:document_to_html_with_options/2"
},
{
"name": "\u0027Elixir.MDExNative.Comrak\u0027:document_to_html/2"
}
],
"repo": "https://github.com/leandrocp/mdex_native",
"vendor": "leandrocp",
"versions": [
{
"lessThan": "0.2.3",
"status": "affected",
"version": "0.1.0",
"versionType": "semver"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:leandrocp:mdex_native:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.MDExNative.Comrak\u0027",
"mdex_native_nif"
],
"packageName": "leandrocp/mdex_native",
"packageURL": "pkg:github/leandrocp/mdex_native",
"product": "mdex_native",
"programFiles": [
"native/mdex_native_nif/src/lumis_adapter.rs"
],
"programRoutines": [
{
"name": "mdex_native_nif::lumis_adapter::LumisAdapter::parse_highlight_lines"
},
{
"name": "\u0027Elixir.MDExNative.Native\u0027:document_to_html_with_options/2"
},
{
"name": "\u0027Elixir.MDExNative.Comrak\u0027:document_to_html/2"
}
],
"repo": "https://github.com/leandrocp/mdex_native",
"vendor": "leandrocp",
"versions": [
{
"lessThan": "798a363b4339f6f7162ec8437c4c9f9b5ae6fbf3",
"status": "affected",
"version": "956528c5e31746253347029e810a969ab916fd27",
"versionType": "git"
}
]
}
],
"configurations": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eExploitation requires the application to enable code-block decorators. Decorators are active only when the render options \u003ctt\u003egithub_pre_lang\u003c/tt\u003e and \u003ctt\u003efull_info_string\u003c/tt\u003e are both set and an inline syntax-highlight formatter (for example \u003ctt\u003e{:html_inline, ...}\u003c/tt\u003e) is configured. Applications that render Markdown with the default options do not parse \u003ctt\u003ehighlight_lines\u003c/tt\u003e specifications and are not affected.\u003c/p\u003e"
}
],
"value": "Exploitation requires the application to enable code-block decorators. Decorators are active only when the render options github_pre_lang and full_info_string are both set and an inline syntax-highlight formatter (for example {:html_inline, ...}) is configured. Applications that render Markdown with the default options do not parse highlight_lines specifications and are not affected."
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*",
"versionEndExcluding": "0.12.3",
"versionStartIncluding": "0.11.0",
"vulnerable": true
}
],
"negate": false,
"operator": "AND"
},
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:leandrocp:mdex_native:*:*:*:*:*:*:*:*",
"versionEndExcluding": "0.2.3",
"versionStartIncluding": "0.1.0",
"vulnerable": true
}
],
"negate": false,
"operator": "AND"
}
],
"operator": "OR"
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Peter Ullrich"
},
{
"lang": "en",
"type": "remediation developer",
"value": "Leandro Pereira"
},
{
"lang": "en",
"type": "analyst",
"value": "Jonatan M\u00e4nnchen / EEF"
}
],
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "Memory Allocation with Excessive Size Value vulnerability in leandrocp mdex allows an unauthenticated attacker to cause a denial of service through unbounded memory allocation.\u003cp\u003e\u003ctt\u003ecomrak_nif::lumis_adapter::LumisAdapter::parse_highlight_lines\u003c/tt\u003e in \u003ctt\u003enative/comrak_nif/src/lumis_adapter.rs\u003c/tt\u003e eagerly expands a user-controlled inclusive line range from a fenced code block\u0027s \u003ctt\u003ehighlight_lines\u003c/tt\u003e decorator into a \u003ctt\u003eVec\u0026lt;usize\u0026gt;\u003c/tt\u003e, pushing one element per integer in the range with no upper bound on the range size. An attacker who can supply Markdown that an application renders with \u003ctt\u003eMDEx.to_html/2\u003c/tt\u003e (for example a comment, chat message, or wiki page) can embed a code block whose info string is \u003ctt\u003erust highlight_lines=\"1-100000000\"\u003c/tt\u003e, forcing the native adapter to allocate roughly 8 bytes per line in the range.\u003c/p\u003e\u003cp\u003eA payload that differs by only a few bytes can therefore allocate hundreds of megabytes, and a sufficiently large range (for example \u003ctt\u003e1-2000000000\u003c/tt\u003e) exhausts host memory and aborts the BEAM, denying service to every user of the rendering process. The per-line write loop additionally tests membership with a linear scan over the same vector, degrading rendering to a quadratic cost even for ranges that do not immediately exhaust memory.\u003c/p\u003e\u003cp\u003eThe vulnerable native code originally shipped inside \u003ctt\u003emdex\u003c/tt\u003e (in \u003ctt\u003enative/comrak_nif/src/lumis_adapter.rs\u003c/tt\u003e) and was later extracted into the separate \u003ctt\u003emdex_native\u003c/tt\u003e package (\u003ctt\u003enative/mdex_native_nif/src/lumis_adapter.rs\u003c/tt\u003e), where it remains unpatched.\u003c/p\u003e\u003cp\u003eThis issue affects mdex from 0.11.0 before 0.12.3, and mdex_native from 0.1.0 before 0.2.3.\u003c/p\u003e"
}
],
"value": "Memory Allocation with Excessive Size Value vulnerability in leandrocp mdex allows an unauthenticated attacker to cause a denial of service through unbounded memory allocation.\n\ncomrak_nif::lumis_adapter::LumisAdapter::parse_highlight_lines in native/comrak_nif/src/lumis_adapter.rs eagerly expands a user-controlled inclusive line range from a fenced code block\u0027s highlight_lines decorator into a Vec\u003cusize\u003e, pushing one element per integer in the range with no upper bound on the range size. An attacker who can supply Markdown that an application renders with MDEx.to_html/2 (for example a comment, chat message, or wiki page) can embed a code block whose info string is rust highlight_lines=\"1-100000000\", forcing the native adapter to allocate roughly 8 bytes per line in the range.\n\nA payload that differs by only a few bytes can therefore allocate hundreds of megabytes, and a sufficiently large range (for example 1-2000000000) exhausts host memory and aborts the BEAM, denying service to every user of the rendering process. The per-line write loop additionally tests membership with a linear scan over the same vector, degrading rendering to a quadratic cost even for ranges that do not immediately exhaust memory.\n\nThe 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.\n\nThis issue affects mdex from 0.11.0 before 0.12.3, and mdex_native from 0.1.0 before 0.2.3."
}
],
"impacts": [
{
"capecId": "CAPEC-130",
"descriptions": [
{
"lang": "en",
"value": "CAPEC-130 Excessive Allocation"
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "LOCAL",
"baseScore": 6.9,
"baseSeverity": "MEDIUM",
"privilegesRequired": "NONE",
"subAvailabilityImpact": "HIGH",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H",
"version": "4.0",
"vulnAvailabilityImpact": "HIGH",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "NONE"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-789",
"description": "CWE-789 Memory Allocation with Excessive Size Value",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-06-29T18:52:36.199Z",
"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"shortName": "EEF"
},
"references": [
{
"tags": [
"vendor-advisory",
"related"
],
"url": "https://github.com/leandrocp/mdex_native/security/advisories/GHSA-j93q-9cvj-rxfm"
},
{
"tags": [
"related"
],
"url": "https://cna.erlef.org/cves/CVE-2026-53428.html"
},
{
"tags": [
"related"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-53428"
},
{
"tags": [
"patch"
],
"url": "https://github.com/leandrocp/mdex_native/commit/798a363b4339f6f7162ec8437c4c9f9b5ae6fbf3"
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "Unbounded memory allocation in highlight_lines range expansion in mdex",
"workarounds": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eDo not enable code-block decorators: leave the \u003ctt\u003egithub_pre_lang\u003c/tt\u003e and \u003ctt\u003efull_info_string\u003c/tt\u003e render options unset, or avoid configuring an inline syntax-highlight formatter, so that \u003ctt\u003ehighlight_lines\u003c/tt\u003e specifications are never parsed.\u003c/p\u003e"
}
],
"value": "Do not enable code-block decorators: leave the github_pre_lang and full_info_string render options unset, or avoid configuring an inline syntax-highlight formatter, so that highlight_lines specifications are never parsed."
}
],
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"assignerShortName": "EEF",
"cveId": "CVE-2026-53428",
"datePublished": "2026-06-29T18:52:36.199Z",
"dateReserved": "2026-06-09T11:01:47.529Z",
"dateUpdated": "2026-06-29T19:17:25.070Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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