high · 7.5 Patched

markdown-it: Quadratic complexity in smartquotes with unmatched closing quotes

CVE-2026-111759 · GHSA-r7fv-28h4-cvq7 · published 20 Oct 2026

How serious is it

  • Severity: high, CVSS score 7.5 out of 10.
  • No exploit prediction (EPSS) score yet.
  • Not on the CISA list of exploited vulnerabilities.
  • No public exploit in Exploit-DB.

Is your app affected by CVE-2026-111759?

Paste this prompt into Claude Code, Cursor or any AI coding tool: it runs a free Shippable scan of your project and fixes what it finds. Built with Lovable, Bolt or v0? Scan your live app. Or upload your package file.

Who is affected

  • markdown-it (npm) >= 15.0.0, < 15.0.2
  • markdown-it (npm) < 14.3.2

How to check

  1. Run npm ls markdown-it in your project to see the installed version, including copies pulled in by other packages.
  2. Or paste your lockfile into the checker: it lists every package with a known vulnerability, this one included.
  3. Or run npx shippable-dev scan localhost:3000 in your project folder. It reads your lockfile and flags this vulnerability along with every other known one.

How to fix

Copies a prompt for Claude Code, Cursor or Codex: it checks your lockfiles for this and upgrades it.
  1. On >= 15.0.0, < 15.0.2: Upgrade markdown-it to 15.0.2 or later, commit the lockfile and redeploy.
  2. On < 14.3.2: Upgrade markdown-it to 14.3.2 or later, commit the lockfile and redeploy.
  3. If a vulnerable version was live, check your logs and rotate the secrets that server could read.

The advisory

### Impact 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. ### Reproduction ```js import MarkdownIt from 'markdown-it' import { performance } from 'node:perf_hooks' const md = new MarkdownIt({ typographer: true }) for (const k of [2000, 4000, 8000, 16000, 32000]) { const input = '"a '.repeat(k) + "b' ".repeat(k) const start = performance.now() md.render(input) console.log(input.length, (performance.now() - start).toFixed(1), 'ms') } ``` Result: |input size|time| |-|-| |12000|18ms| |24000|47ms| |48000|115ms| |96000|428ms| |192000|1586ms| ### Patches Fixed in **15.0.2** and **14.3.2**. ### Workarounds Disable typography with `typographer: false`, or disable only the smartquotes rule: ```js md.disable('smartquotes') ```

Check your whole app

Dependencies are only half of it. Free and read-only: before you push, run npx shippable-dev scan localhost:3000 in your project folder, no account needed. For your live app, you prove it's yours with a one-line tag first.

References

Merged from GitHub Advisory Database. Last updated 23 Oct 2026. All vulnerabilities · RSS · JSON

Get alerts for new exploited vulnerabilities