8.7

CVE-2026-86434

commonmark 2.0.0 through 2.8.3 Denial of Service via Slug Collision

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.
Daten sind bereitgestellt durch das CVE Programm von einer CVE Numbering Authority (CNA) (Unstrukturiert).
Herstellerthephpleague
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Produkt commonmark
Default Statusunaffected
Version 2.0.0
Version < 2.8.4
Status affected
Version 2.8.4
Status unaffected
VulnDex Vulnerability Enrichment
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Zu dieser CVE wurde keine Warnung gefunden.
EPSS Metriken
Typ Quelle Score Percentile
EPSS FIRST.org 0.29% 0.214
CVSS Metriken
Quelle Base Score Exploit Score Impact Score Vector String
disclosure@vulncheck.com 8.7 0 0
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
disclosure@vulncheck.com 7.5 3.9 3.6
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE-407 Inefficient Algorithmic Complexity

An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.

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