CVE-2026-53426

Summary

Allocation of Resources Without Limits or Throttling vulnerability in leandrocp MDEx allows Excessive Allocation.

MDEx.parse_document/2 accepts a {:json, json} source. In lib/mdex.ex, the private json_to_node/1 function passes the attacker-controlled node_type value to Module.concat/1, which calls String.to_atom/1 and interns a brand-new atom for every distinct value. Atoms are never garbage collected on the BEAM, so a crafted JSON document carrying a unique node_type at each (deeply nested) node mints one permanent atom per node.

A single document can intern hundreds of thousands of atoms, and a large enough document exhausts the default atom table (around 1,048,576 atoms) and aborts the entire Erlang VM, taking down every process on the node. Any application that passes untrusted input to the {:json, …} source of MDEx.parse_document is exposed to an unauthenticated denial-of-service.

This issue affects mdex from 0.4.3 before 0.13.2.

Affected Software

VendorProductVersion RangeStatus
leandrocpmdex0.4.3 < 0.13.2affected
leandrocpmdexcbb59a3f792dbc343873adec3466f49c853dc309 < 00fddf444220a1f1cc0af0a1cab6738804878387affected

Weaknesses

  • CWE-770: CWE-770 Allocation of Resources Without Limits or Throttling

Workarounds

Do not pass untrusted or attacker-controlled input to the {:json, …} source of MDEx.parse_document/2. The {:markdown, …} source is not affected.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References