CVE-2025-6493 CodeMirror Markdown Mode markdown.js redos
Remote attackers can cause denial of service in CodeMirror Markdown Mode via inefficient regular expression complexity.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2025-6493?
CVE-2025-6493 is a medium-severity denial of service vulnerability in CodeMirror, published on 22 Jun 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A weakness has been identified in CodeMirror up to 5.65.20. Affected is an unknown function of the file mode/markdown/markdown.js of the component Markdown Mode. This manipulation causes inefficient regular expression complexity. It is possible to initiate the attack remotely. The exploit has been made available to the public and could be exploited. Upgrading to version 6.0 is able to address this issue. You should upgrade the affected component. Not all code samples mentioned in the GitHub issue can be found. The repository mentions, that "CodeMirror 6 exists, and is [...] much more actively maintained."
Which versions are affected by CVE-2025-6493?
How do I fix CVE-2025-6493?
No fix has been published for CVE-2025-6493 yet. Limit exposure of the affected software until one is available.
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-2025-6493 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-6493 exists.
Sources
Also known as DEBIAN-CVE-2025-6493, GHSA-pff4-9qxc-79mq, UBUNTU-CVE-2025-6493.