{"id":"CVE-2026-53428","state":"PUBLISHED","title":"Unbounded memory allocation in highlight_lines range expansion in mdex","description":"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'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.\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.","publishedAt":"2026-06-29T18:52:36.199Z","updatedAt":"2026-06-30T04:38:36.755Z","severity":{"score":6.9,"label":"Medium","version":"4.0","vector":"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","source":"EEF"},"assigner":"EEF","products":["leandrocp mdex","leandrocp mdex_native"],"affected":[{"vendor":"leandrocp","product":"mdex","packageName":"mdex","packageURL":"pkg:hex/mdex","defaultStatus":"unaffected","versions":[{"version":"0.11.0","status":"affected","lessThan":"0.12.3","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*"],"modules":["'Elixir.MDEx'","comrak_nif"],"programFiles":["native/comrak_nif/src/lumis_adapter.rs"],"programRoutines":[{"name":"comrak_nif::lumis_adapter::LumisAdapter::parse_highlight_lines"},{"name":"'Elixir.MDEx':to_html/2"}],"repo":"https://github.com/leandrocp/mdex"},{"vendor":"leandrocp","product":"mdex","packageName":"leandrocp/mdex","packageURL":"pkg:github/leandrocp/mdex","defaultStatus":"unaffected","versions":[{"version":"a8407611715d1ead35fbcba79c72cef1b7df387b","status":"affected","lessThan":"6ed94d905f97af188323f042698ae841c02293b4","versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*"],"modules":["'Elixir.MDEx'","comrak_nif"],"programFiles":["native/comrak_nif/src/lumis_adapter.rs"],"programRoutines":[{"name":"comrak_nif::lumis_adapter::LumisAdapter::parse_highlight_lines"},{"name":"'Elixir.MDEx':to_html/2"}],"repo":"https://github.com/leandrocp/mdex"},{"vendor":"leandrocp","product":"mdex_native","packageName":"mdex_native","packageURL":"pkg:hex/mdex_native","defaultStatus":"unaffected","versions":[{"version":"0.1.0","status":"affected","lessThan":"0.2.3","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:leandrocp:mdex_native:*:*:*:*:*:*:*:*"],"modules":["'Elixir.MDExNative.Comrak'","mdex_native_nif"],"programFiles":["native/mdex_native_nif/src/lumis_adapter.rs"],"programRoutines":[{"name":"mdex_native_nif::lumis_adapter::LumisAdapter::parse_highlight_lines"},{"name":"'Elixir.MDExNative.Native':document_to_html_with_options/2"},{"name":"'Elixir.MDExNative.Comrak':document_to_html/2"}],"repo":"https://github.com/leandrocp/mdex_native"},{"vendor":"leandrocp","product":"mdex_native","packageName":"leandrocp/mdex_native","packageURL":"pkg:github/leandrocp/mdex_native","defaultStatus":"unaffected","versions":[{"version":"956528c5e31746253347029e810a969ab916fd27","status":"affected","lessThan":"798a363b4339f6f7162ec8437c4c9f9b5ae6fbf3","versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:leandrocp:mdex_native:*:*:*:*:*:*:*:*"],"modules":["'Elixir.MDExNative.Comrak'","mdex_native_nif"],"programFiles":["native/mdex_native_nif/src/lumis_adapter.rs"],"programRoutines":[{"name":"mdex_native_nif::lumis_adapter::LumisAdapter::parse_highlight_lines"},{"name":"'Elixir.MDExNative.Native':document_to_html_with_options/2"},{"name":"'Elixir.MDExNative.Comrak':document_to_html/2"}],"repo":"https://github.com/leandrocp/mdex_native"}],"references":["https://github.com/leandrocp/mdex_native/security/advisories/GHSA-j93q-9cvj-rxfm","https://cna.erlef.org/cves/CVE-2026-53428.html","https://osv.dev/vulnerability/EEF-CVE-2026-53428","https://github.com/leandrocp/mdex_native/commit/798a363b4339f6f7162ec8437c4c9f9b5ae6fbf3"],"weaknesses":["CWE-789"],"ingestedAt":"2026-10-29T20:12:16.098Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/53xxx/CVE-2026-53428.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-53428","state":"PUBLISHED","datePublished":"2026-06-29T18:52:36.199Z","dateUpdated":"2026-06-30T04:38:36.755Z","assignerShortName":"EEF","assignerOrgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateReserved":"2026-06-09T11:01:47.529Z"},"containers":{"cna":{"title":"Unbounded memory allocation in highlight_lines range expansion in mdex","descriptions":[{"lang":"en","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'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.\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."}],"affected":[{"vendor":"leandrocp","product":"mdex","packageName":"mdex","packageURL":"pkg:hex/mdex","defaultStatus":"unaffected","versions":[{"version":"0.11.0","status":"affected","lessThan":"0.12.3","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*"],"modules":["'Elixir.MDEx'","comrak_nif"],"programFiles":["native/comrak_nif/src/lumis_adapter.rs"],"programRoutines":[{"name":"comrak_nif::lumis_adapter::LumisAdapter::parse_highlight_lines"},{"name":"'Elixir.MDEx':to_html/2"}],"repo":"https://github.com/leandrocp/mdex"},{"vendor":"leandrocp","product":"mdex","packageName":"leandrocp/mdex","packageURL":"pkg:github/leandrocp/mdex","defaultStatus":"unaffected","versions":[{"version":"a8407611715d1ead35fbcba79c72cef1b7df387b","status":"affected","lessThan":"6ed94d905f97af188323f042698ae841c02293b4","versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*"],"modules":["'Elixir.MDEx'","comrak_nif"],"programFiles":["native/comrak_nif/src/lumis_adapter.rs"],"programRoutines":[{"name":"comrak_nif::lumis_adapter::LumisAdapter::parse_highlight_lines"},{"name":"'Elixir.MDEx':to_html/2"}],"repo":"https://github.com/leandrocp/mdex"},{"vendor":"leandrocp","product":"mdex_native","packageName":"mdex_native","packageURL":"pkg:hex/mdex_native","defaultStatus":"unaffected","versions":[{"version":"0.1.0","status":"affected","lessThan":"0.2.3","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:leandrocp:mdex_native:*:*:*:*:*:*:*:*"],"modules":["'Elixir.MDExNative.Comrak'","mdex_native_nif"],"programFiles":["native/mdex_native_nif/src/lumis_adapter.rs"],"programRoutines":[{"name":"mdex_native_nif::lumis_adapter::LumisAdapter::parse_highlight_lines"},{"name":"'Elixir.MDExNative.Native':document_to_html_with_options/2"},{"name":"'Elixir.MDExNative.Comrak':document_to_html/2"}],"repo":"https://github.com/leandrocp/mdex_native"},{"vendor":"leandrocp","product":"mdex_native","packageName":"leandrocp/mdex_native","packageURL":"pkg:github/leandrocp/mdex_native","defaultStatus":"unaffected","versions":[{"version":"956528c5e31746253347029e810a969ab916fd27","status":"affected","lessThan":"798a363b4339f6f7162ec8437c4c9f9b5ae6fbf3","versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:leandrocp:mdex_native:*:*:*:*:*:*:*:*"],"modules":["'Elixir.MDExNative.Comrak'","mdex_native_nif"],"programFiles":["native/mdex_native_nif/src/lumis_adapter.rs"],"programRoutines":[{"name":"mdex_native_nif::lumis_adapter::LumisAdapter::parse_highlight_lines"},{"name":"'Elixir.MDExNative.Native':document_to_html_with_options/2"},{"name":"'Elixir.MDExNative.Comrak':document_to_html/2"}],"repo":"https://github.com/leandrocp/mdex_native"}],"references":[{"url":"https://github.com/leandrocp/mdex_native/security/advisories/GHSA-j93q-9cvj-rxfm","tags":["vendor-advisory","related"]},{"url":"https://cna.erlef.org/cves/CVE-2026-53428.html","tags":["related"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-53428","tags":["related"]},{"url":"https://github.com/leandrocp/mdex_native/commit/798a363b4339f6f7162ec8437c4c9f9b5ae6fbf3","tags":["patch"]}],"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":{"shortName":"EEF","orgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateUpdated":"2026-06-30T04:38:36.755Z"},"configurations":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"<p>Exploitation requires the application to enable code-block decorators. Decorators are active only when the render options <tt>github_pre_lang</tt> and <tt>full_info_string</tt> are both set and an inline syntax-highlight formatter (for example <tt>{:html_inline, ...}</tt>) is configured. Applications that render Markdown with the default options do not parse <tt>highlight_lines</tt> specifications and are not affected.</p>"}],"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 Männchen / EEF"}],"impacts":[{"capecId":"CAPEC-130","descriptions":[{"lang":"en","value":"CAPEC-130 Excessive Allocation"}]}],"source":{"discovery":"EXTERNAL"},"workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"<p>Do not enable code-block decorators: leave the <tt>github_pre_lang</tt> and <tt>full_info_string</tt> render options unset, or avoid configuring an inline syntax-highlight formatter, so that <tt>highlight_lines</tt> specifications are never parsed.</p>"}],"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"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-06-29T19:17:11.005816Z","id":"CVE-2026-53428","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-06-29T19:17:25.070Z"}}]}}}