CVE intelligence and bounded remediation

CVE-2026-53429 — Missing Release of Memory after Effective Lifetime vulnerability in leandrocp mdex and mdex_native allows an attacker who controls a...

Medium CVSS 6.9

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 dir…

Severity
Medium
CVSS
6.9 (4.0)
Published
2026-06-29
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-401

Affected products

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Matched remediation archetype

Resource exhaustion and denial of service

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Check exposure

  • Identify attacker-influenced work factors including input size, nesting, compression, fan-out, regex cost, allocation, recursion, retries, and connection lifetime.
  • Map per-request and shared CPU, memory, disk, descriptor, thread, queue, and downstream-service limits.
  • Determine whether authentication, tenancy, quotas, and rate controls apply before expensive processing begins.

Remediate safely

  • Bound input size, nesting, expansion, work, concurrency, queue depth, retries, and execution time before resource-intensive processing.
  • Release resources on every success, error, cancellation, and timeout path and use backpressure instead of unbounded buffering.
  • Update affected components and add small deterministic tests that assert resource ceilings rather than exhausting a host.

Authoritative sources

Complete CVE record and remediation plan

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