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VulnerabilityPublished

CVE-2026-54888: leandrocp mdex · Uncontrolled Recursion

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 8 Nov 2026, 23:24 UTC

CVSS 4.0 base score
6.9Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 14% 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 10 Nov 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
leandrocpmdexAffected
  • >=0.3.0 <0.12.3
Fixed in
  • 0.12.3
leandrocpmdexAffected
  • ≥ d0bc7d55177727c61d188ef465178ab3b81f4f2c, < 6ed94d905f97af188323f042698ae841c02293b4
Fixed in
  • 6ed94d905f97af188323f042698ae841c02293b4
leandrocpmdex_nativeAffected
  • >=0.1.0 <0.2.3
Fixed in
  • 0.2.3
leandrocpmdex_nativeAffected
  • ≥ 956528c5e31746253347029e810a969ab916fd27, < 947696c47bc22bea5dffc0f78c946fa6b70ce183
Fixed in
  • 947696c47bc22bea5dffc0f78c946fa6b70ce183
Hexmdexpkg:hex/mdexOther threatsAffected
  • >=0.3.0 <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 untrusted Markdown input with mdex or mdex_native versions affected by this vulnerability. Consider applying input validation or limiting recursion depth externally if possible.

Description

Uncontrolled Recursion vulnerability in leandrocp mdex allows denial of service via deeply nested Markdown input. mdex converts between an Elixir %MDEx.Document{} struct and Comrak's internal AST using two mutually recursive Rust functions, ex_document_to_comrak_ast and comrak_ast_to_ex_document, in the NIF source file document.rs. Neither function enforces a maximum nesting depth, so the recursion depth is bounded only by the structure of the input. An attacker who can get a Markdown document rendered (for example through MDEx.parse_document!/1 or MDEx.to_html/1) can supply a document with thousands of nested block quotes, which drives unbounded recursion across the NIF boundary and exhausts the native C stack. Because the resulting stack overflow is an uncatchable SIGSEGV raised inside a NIF, it cannot be contained by the Erlang runtime. It terminates the operating system process running the BEAM, killing every Elixir and Erlang process on the node, not just the caller that triggered the render. No authentication or special privileges are required. The vulnerable conversion code was extracted from mdex into the separate mdex_native package starting in mdex 0.12.3. This issue affects mdex from 0.3.0 before 0.12.3 and mdex_native from 0.1.0 before 0.2.3.

References

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