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
EEF
CNA
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 | |
|---|---|---|---|
| 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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"credits": [
{
"lang": "en",
"type": "finder",
"value": "Peter Ullrich"
},
{
"lang": "en",
"type": "remediation developer",
"value": "Leandro Pereira"
},
{
"lang": "en",
"type": "analyst",
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"descriptions": [
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"lang": "en",
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"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"
}
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"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."
}
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"attackRequirements": "PRESENT",
"attackVector": "LOCAL",
"baseScore": 6.9,
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"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": [
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"lang": "en",
"value": "GENERAL"
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]
}
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"descriptions": [
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"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"
},
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"tags": [
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"url": "https://github.com/leandrocp/mdex_native/security/advisories/GHSA-j93q-9cvj-rxfm"
},
{
"tags": [
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"url": "https://cna.erlef.org/cves/CVE-2026-53428.html"
},
{
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"url": "https://osv.dev/vulnerability/EEF-CVE-2026-53428"
},
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"url": "https://github.com/leandrocp/mdex_native/commit/798a363b4339f6f7162ec8437c4c9f9b5ae6fbf3"
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "Unbounded memory allocation in highlight_lines range expansion in mdex",
"workarounds": [
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"lang": "en",
"supportingMedia": [
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],
"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": {
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"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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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
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.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
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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.