CVE-2026-49851Mistune: Potential DoS via quadratic-time parsing in parse_link_text

Descripción

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, Mistune is vulnerable to a CPU exhaustion DoS due to superlinear (approximately O(n²)) behavior in parse_link_text. When parsing Markdown containing many consecutive [ characters, parse_link_text repeatedly scans the input using a regex search inside a loop. Each iteration re-scans a large portion of the remaining string, resulting in quadratic-time behavior. An attacker-controlled Markdown input can therefore trigger excessive CPU usage with a very small payload. This vulnerability is fixed in 3.3.0.

Datos: CVE.org, NVD, CISA KEV, FIRST EPSS, Ubuntu. Se publican tal como los indican las fuentes, en inglés.

Productos y versiones afectados

Referencias y parches

• https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p
• https://access.redhat.com/errata/RHSA-2026:60520
• https://access.redhat.com/security/cve/CVE-2026-49851
• https://bugzilla.redhat.com/show_bug.cgi?id=2492304
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49851.json