CVE-2025-9670 mixmark-io turndown commonmark-rules.js redos
Remote attackers can cause denial of service in the turndown library via inefficient regular expressions in commonmark-rules.js.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-9670?
CVE-2025-9670 is a medium-severity denial of service vulnerability in mixmark-io turndown, published on 29 Aug 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A security flaw has been discovered in mixmark-io turndown up to 7.2.1. This affects an unknown function of the file src/commonmark-rules.js. Performing manipulation results in inefficient regular expression complexity. It is possible to initiate the attack remotely. The exploit has been released to the public and may be exploited.
Which versions are affected by CVE-2025-9670?
How do I fix CVE-2025-9670?
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-2025-9670 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-9670 exists.
Sources
Also known as DEBIAN-CVE-2025-9670, GHSA-6jxv-35jp-jr5v, UBUNTU-CVE-2025-9670.