leandrocp mdex/mdex_native up to 0.12.2 document.rs Box::leak memory leak

Summaryinfo

A vulnerability marked as problematic has been reported in leandrocp mdex and mdex_native up to 0.12.2. Affected by this vulnerability is the function Box::leak of the file native/comrak_nif/src/types/document.rs. The manipulation leads to memory leak. This vulnerability is listed as CVE-2026-53429. The attack must be carried out locally. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in leandrocp mdex and mdex_native up to 0.12.2 and classified as problematic. This issue affects the function Box::leak of the file native/comrak_nif/src/types/document.rs. The manipulation with an unknown input leads to a memory leak vulnerability. Using CWE to declare the problem leads to CWE-401. The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory. Impacted is availability. The summary by CVE is:

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 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.

The weakness was presented by Peter Ullrich and Jonatan Männchen as GHSA-cmvp-gp9f-23xw. The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-53429 since 06/09/2026. The exploitation is known to be easy. An attack has to be approached locally. Technical details are known, but no exploit is available.

Upgrading to version 0.12.3 eliminates this vulnerability. Applying the patch 6ed94d905f97af188323f042698ae841c02293b4 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Vendor

• leandrocp

Name

• mdex
• mdex_native

Version

• 0.12.0
• 0.12.1
• 0.12.2

License

• open-source

CPE 2.3info

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CPE 2.2info

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