Is CVE-2026-86428 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-86428?

CVE-2026-86428 has a CVSS v3 severity of HIGH (7.5).

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CVE-2026-86428

Description

commonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the AttributesExtension when processing distinctly-named attributes. Attackers can submit Markdown with numerous distinct attribute names to cause quadratic-time attribute merging and filtering, consuming disproportionate CPU resources and preventing legitimate requests from completing.