Quick answers
- Is CVE-2026-53428 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-53428 being exploited in the wild.
- How severe is CVE-2026-53428?
- Informational severity, with a CVSS score of 6.9, published 29 June 2026.
- Which products and versions are affected?
- Leandrocp Mdex >= 0.11.0, < 0.12.3; Leandrocp Mdex Native >= 0.1.0, < 0.2.3.
- Is there a fix for CVE-2026-53428?
- A patch was published on 2026-06-29: Fixed in mdex 0.12.3 and mdex_native 0.2.3 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-53428 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-53428?
- Check whether you run Leandrocp Mdex or Leandrocp Mdex Native at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability exists in the `parse_highlight_lines` routine within `lumis_adapter.rs`. The code eagerly expands user-controlled inclusive line ranges (e.g., '1-100000000') into a `Vec<usize>` without upper-bound validation. This results in approximately 8 bytes of allocation per integer in the range. An attacker can provide a large range in a Markdown fenced code block's `highlight_lines` decorator to exhaust host memory and abort the BEAM process. Exploitation requires `github_pre_lang` and `full_info_string` options to be enabled alongside an inline syntax-highlight formatter. The issue was fixed in mdex 0.12.3 and mdex_native 0.2.3.
Affected products
- leandrocp mdex >= 0.11.0, < 0.12.3
- leandrocp mdex_native >= 0.1.0, < 0.2.3
Timeline
- 2026-06-29: disclosed
- 2026-06-29: patched: Fixed in mdex 0.12.3 and mdex_native 0.2.3
- 2026-06-29: advisory