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CVE-2026-53429— Unbounded native memory leak in mdex escaped-tag rendering enables unauthenticated denial of service

Quick assessment

Affected
leandrocp mdex
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Leandro Pereira MDExNative是加拿大Leandro Pereira个人开发者开源的一个服务器支撑系统。 Leandro Pereira MDExNative存在资源管理错误漏洞，该漏洞源于有效生命周期后内存未释放问题，可能导致控制已渲染文档的攻击者通过无界本机内存耗尽造成拒绝服务。

AI Predicted 7.5 Difficulty: Easy EPSS 0.18% · P7

Affected Version Matrix 4

VendorProduct Version RangeStatus
leandrocp mdex 0.11.0< 0.12.3 affected
81e4d14dd3aa5b206e395c7f372b9b413793015f< 6ed94d905f97af188323f042698ae841c02293b4 affected
leandrocp mdex_native 0.1.0< 0.2.3 affected
956528c5e31746253347029e810a969ab916fd27< cbd927fb5061b488de8d90a8ef6df65718ca1fe6 affected
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I. Basic Information for CVE-2026-53429

Vulnerability Information
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Vulnerability Title
Unbounded native memory leak in mdex escaped-tag rendering enables unauthenticated denial of service
Source: CVE Program / CVE List V5
Vulnerability Description
Missing Release of Memory after Effective Lifetime vulnerability in leandrocp mdex and mdex_native allows an attacker who controls a rendered document to cause a denial of service through unbounded native memory exhaustion. The native rendering code permanently leaks memory when rendering a document that contains escaped-tag nodes. The conversion of each %MDEx.EscapedTag{} node into its native representation (From<ExEscapedTag> for NodeValue in the Rust NIF) calls Box::leak on the caller-supplied literal string, which surrenders the backing allocation so that it lives for the entire lifetime of the operating system process and is never freed. Both the byte length of each literal and the number of escaped-tag nodes in a document are attacker-controlled, and there is no size cap, rate limit, or string interning on this path. Every render of a document containing escaped-tag nodes therefore leaks literal_size x node_count bytes that can never be reclaimed, and repeated renders accumulate without bound. Rendering reaches this path through the public MDEx.to_html/1 entry point and any other API that renders a supplied %MDEx.Document{}. Any application that uses mdex (or mdex_native directly) to render documents derived from user-supplied content is affected. Because the leaked memory is never reclaimed for the life of the BEAM process, an attacker can drive resident memory upward without limit until the node exhausts memory and crashes, taking down every process on it. The vulnerable native code originally shipped inside mdex (in native/comrak_nif/src/types/document.rs) and was later extracted into the separate mdex_native package (native/mdex_native_nif/src/types/document.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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
在移除最后引用时对内存的释放不恰当(内存泄露)
Source: CVE Program / CVE List V5
Vulnerability Title
Leandro Pereira MDExNative 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Leandro Pereira MDExNative是加拿大Leandro Pereira个人开发者开源的一个服务器支撑系统。 Leandro Pereira MDExNative存在资源管理错误漏洞，该漏洞源于有效生命周期后内存未释放问题，可能导致控制已渲染文档的攻击者通过无界本机内存耗尽造成拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
leandrocp mdex 0.11.0 ~ 0.12.3 cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*
leandrocp mdex 81e4d14dd3aa5b206e395c7f372b9b413793015f ~ 6ed94d905f97af188323f042698ae841c02293b4 cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*
leandrocp mdex_native 0.1.0 ~ 0.2.3 cpe:2.3:a:leandrocp:mdex_native:*:*:*:*:*:*:*:*
leandrocp mdex_native 956528c5e31746253347029e810a969ab916fd27 ~ cbd927fb5061b488de8d90a8ef6df65718ca1fe6 cpe:2.3:a:leandrocp:mdex_native:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-53429

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III. Intelligence Information for CVE-2026-53429

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Patches & Fixes for CVE-2026-53429 (1)

Vendor Advisories for CVE-2026-53429 (3)

Same Patch Batch · leandrocp · 2026-06-29 · 6 CVEs total

CVE-2026-53426 Atom-table exhaustion denial-of-service via JSON parse_document in MDEx
CVE-2026-53428 Unbounded memory allocation in highlight_lines range expansion in mdex
CVE-2026-53427 Cross-site scripting in MDEx via unescaped highlight_lines_class code-fence attribute
CVE-2026-54888 Uncontrolled recursion over deeply nested Markdown crashes the BEAM in mdex
CVE-2026-54889 Unsanitized URL schemes in MDEx Quill Delta output allow javascript: injection (XSS)

IV. Related Vulnerabilities

Same product: mdex
Same vendor: leandrocp
Same weakness: CWE-401