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 O(K^2) time complexity for K headings that collapse to the same base slug. The vulnerable path is reached when HeadingPermalinkExtension, FootnoteExtension, or TableOfContentsExtension is registered. An unauthenticated attacker can force many headings onto a single base slug (e.g., via empty ATX headings, identical heading text, or punctuation-only headings) in a small Markdown document, consuming excessive CPU and denying service.

• CWE-407

• https://github.com/thephpleague/commonmark/security/advisories/GHSA-mh25-x5hq-wrqp
• https://www.vulncheck.com/advisories/commonmark-2.0.0-through-2.8.3-denial-of-service-via-slug-collision

Published

Sep 7, 2026

Last Modified

Sep 8, 2026

Status

Undergoing Analysis

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2026-86429The league/commonmark (thephpleague/commonmark) library in v…7.5
• CVE-2026-8643pip would treat console_scripts and gui_scripts as paths ins…5.5
• CVE-2026-86430league/commonmark versions before 2.9.1 contain multiple den…7.5
• CVE-2026-86431league/commonmark (thephpleague/commonmark) versions >= 2.7.…7.2
• CVE-2026-86432commonmark versions from 2.0.0 before 2.8.4 contain a denial…5.3
• CVE-2026-86433commonmark versions from 1.5.0 before 2.8.4 contain a denial…7.5
• CVE-2026-86435commonmark versions from 1.5.0 before 2.8.4 contain a denial…7.5
• CVE-2026-86436Lara Dashboard before 1.3.2 fails to authorize access to the…5.4
• CVE-2026-86437Lara Dashboard before 1.3.2 authorizes the POST /admin/setti…7.2
• CVE-2026-86438Lara Dashboard before 1.3.2 fails to authorize the Marketpla…7.2
• CVE-2026-86439knowns versions before 0.30.0 fail to validate filesystem pa…8.8
• CVE-2026-8644IBM WebSphere Application Server 9.0, and 8.5 is vulnerable …9.1