Vulnerability · Published Oct 8, 2026 · Assigned by VulnCheck

CVE-2026-105830league/commonmark 2.0.0 before 2.10.2 Quadratic DoS via TableStartParser

High 7.5

In plain English

A high-severity uncontrolled resource consumption in commonmark from thephpleague. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 31% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.4%top 69.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

league/commonmark from 2.0.0 before 2.10.2 contains a quadratic-time denial of service vulnerability in the GitHub Flavored Markdown Table extension's TableStartParser::tryStart() block-start scan. Unauthenticated attackers can submit a large paragraph of pipe-free lines not starting with letters, forcing repeated full-buffer strpos scans that exhaust PHP worker CPU.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	php-league-commonmark	no fix listed	DEBIAN-CVE-2026-105830
Debian:13	php-league-commonmark	no fix listed	DEBIAN-CVE-2026-105830
Debian:14	php-league-commonmark	2.10.3-1	DEBIAN-CVE-2026-105830
Packagist	league/commonmark	2.10.2	GHSA-3q6v-r5mr-hxv8
Ubuntu:26.04:LTS	php-league-commonmark	no fix listed	UBUNTU-CVE-2026-105830
Ubuntu:26.10	php-league-commonmark	no fix listed	UBUNTU-CVE-2026-105830

Affected products (as reported)

Vendor	Product	Versions
thephpleague	commonmark	2.0.0 – before 2.10.2

Weakness: CWE-400 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

GitHub Security Advisory (GHSA-3q6v-r5mr-hxv8) vendor-advisory
VulnCheck Advisory: league/commonmark 2.0.0 before 2.10.2 Quadratic DoS via TableStartParser third-party-advisory