CVE-2026-86434

league/commonmark versions = 2.0.0 and 2.8.4 patched in 2.9.0 contain a denial of service vulnerability in UniqueSlugNormalizer::normalize, which restarts its numeric-suffix search from 1 on every slug collision, resulting in OK^2 time complexity for K headings that collapse to the same base slug...

CVE-2026-86434

league/commonmark (PHP) versions ≥ 2.0.0 and

PT-2026-86800

league/commonmark versions = 2.0.0 and 2.8.4 patched in 2.9.0 contain a denial of service vulnerability in UniqueSlugNormalizer::normalize, which restarts its numeric-suffix search from 1 on every slug collision, resulting in OK^2 time complexity for K headings that collapse to the same base slug...