PT-2026-53681 · Git+1 · Mdex+1
Leandro Pereira
+1
·
Publicado
2026-06-29
·
Atualizado
2026-06-29
·
CVE-2026-53428
CVSS v4.0
6.9
Média
| Vetor | AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H |
Summary
Memory Allocation with Excessive Size Value vulnerability in leandrocp mdex allows an unauthenticated attacker to cause a denial of service through unbounded memory allocation.
comrak nif::lumis adapter::LumisAdapter::parse highlight lines in native/comrak nif/src/lumis adapter.rs eagerly expands a user-controlled inclusive line range from a fenced code block's highlight lines decorator into a Vec, pushing one element per integer in the range with no upper bound on the range size. An attacker who can supply Markdown that an application renders with MDEx.to html/2 (for example a comment, chat message, or wiki page) can embed a code block whose info string is rust highlight lines="1-100000000", forcing the native adapter to allocate roughly 8 bytes per line in the range.
A payload that differs by only a few bytes can therefore allocate hundreds of megabytes, and a sufficiently large range (for example 1-2000000000) exhausts host memory and aborts the BEAM, denying service to every user of the rendering process. The per-line write loop additionally tests membership with a linear scan over the same vector, degrading rendering to a quadratic cost even for ranges that do not immediately exhaust memory.
The vulnerable native code originally shipped inside mdex (in native/comrak nif/src/lumis adapter.rs) and was later extracted into the separate mdex native package (native/mdex native nif/src/lumis adapter.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.
Workaround
Do not enable code-block decorators: leave the github pre lang and full info string render options unset, or avoid configuring an inline syntax-highlight formatter, so that highlight lines specifications are never parsed.
Configuration
Exploitation requires the application to enable code-block decorators. Decorators are active only when the render options github pre lang and full info string are both set and an inline syntax-highlight formatter (for example {:html inline, ...}) is configured. Applications that render Markdown with the default options do not parse highlight lines specifications and are not affected.
Correção
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Enumeração de Fraquezas
Identificadores relacionados
Produtos afetados
Mdex
Mdex Native