CVE-2026-111759 markdown-it: Quadratic complexity in smartquotes with unmatched closing quotes
Attackers can cause denial of service in applications using markdown-it with typographer enabled by submitting crafted Markdown input.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-111759?
CVE-2026-111759 is a high-severity denial of service vulnerability in markdown-it, published on 19 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
markdown-it is a Markdown parser. Prior to 14.3.2 and 15.0.2, when typographer: true is enabled, specially crafted Markdown can cause quadratic processing time in the smartquotes rule, potentially leading to denial of service in applications processing untrusted input. Many opening double quotes followed by unmatched closing single quotes cause repeated scans of the entire opener stack. The same issue occurs with the quote types reversed. The default configuration (typographer: false) is not affected, but this option is enabled with high probability. This issue is fixed in versions 14.3.2 and 15.0.2.
Which versions are affected by CVE-2026-111759?
4 open source packages ship an affected version, including markdown-it.
| Package | Affected | Fixed in |
|---|---|---|
markdown-it npm | All versions | 14.3.2 |
markdown-it npm | All versions | 14.3.2 |
markdown-it npm | From 15.0.0 | 15.0.2 |
markdown-it npm | From 15.0.0 | 15.0.2 |
How do I fix CVE-2026-111759?
Upgrade markdown-it to a fixed version for your release line: 14.3.2 or 15.0.2.
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-2026-111759 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-111759 exists.
Sources
Also known as CLSA-2026-1792518269, CLSA-2026-1792523617, CLSA-2026-1792575285, CLSA-2026-1792587416, CLSA-2026-1792596594, CLSA-2026-1793102413 and 5 more.