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VulnerabilityPublished

CVE-2026-53429: leandrocp mdex · Memory Leak

Affects leandrocp mdexSource CVE Database V5

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Not known to be exploited · CVSS 6.9 Medium : upgrade to 0.12.3 when convenient.

Data as of 10 Nov 2026, 23:24 UTC

CVSS 4.0 base score
6.9Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 0.12.3, 6ed94d905f97af188323f042698ae841c02293b4, 0.2.3 +1
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 29 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 11 Nov 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
leandrocpmdexAffected
  • >=0.11.0 <0.12.3
Fixed in
  • 0.12.3
leandrocpmdexAffected
  • ≥ 81e4d14dd3aa5b206e395c7f372b9b413793015f, < 6ed94d905f97af188323f042698ae841c02293b4
Fixed in
  • 6ed94d905f97af188323f042698ae841c02293b4
leandrocpmdex_nativeAffected
  • >=0.1.0 <0.2.3
Fixed in
  • 0.2.3
leandrocpmdex_nativeAffected
  • ≥ 956528c5e31746253347029e810a969ab916fd27, < cbd927fb5061b488de8d90a8ef6df65718ca1fe6
Fixed in
  • cbd927fb5061b488de8d90a8ef6df65718ca1fe6
Hexmdexpkg:hex/mdexOther threatsAffected
  • >=0.11.0 <0.12.3
Fixed in
  • 0.12.3
Hexmdex_nativepkg:hex/mdex_nativeOther threatsAffected
  • >=0.1.0 <0.2.3
Fixed in
  • 0.2.3

CPE configurations (2)

  • cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*
  • cpe:2.3:a:leandrocp:mdex_native:*:*:*:*:*:*:*:*

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, avoid rendering user-supplied documents containing escaped-tag nodes with mdex or mdex_native to prevent exploitation of this memory leak 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.

References

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