CVE-2026-86432 commonmark 2.0.0 before 2.8.4 Denial of Service via XML
Attackers can cause denial of service in the commonmark PHP library by submitting deeply nested Markdown, leading to excessive memory consumption.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-86432?
CVE-2026-86432 is a medium-severity denial of service vulnerability in thephpleague commonmark, published on 7 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
commonmark versions from 2.0.0 before 2.8.4 contain a denial of service vulnerability in XmlRenderer that emits depth-proportional indentation for every XML tag. Attackers can provide deeply nested Markdown or AST structures to cause quadratic memory consumption and output amplification, exhausting server resources.
Weakness: CWE-405
Which versions are affected by CVE-2026-86432?
How do I fix CVE-2026-86432?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-86432 being exploited?
There is no known exploitation of CVE-2026-86432 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-86432, GHSA-f58g-hmv8-g97m, UBUNTU-CVE-2026-86432.