CVE-2026-111759 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in markdown-it. A fix is available for markdown-it — see the affected versions and patch details below.
markdown-it: Quadratic complexity in smartquotes with unmatched closing quotes
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-111759.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-111759 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
markdown-itnpmDescription
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
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:
md.disable('smartquotes')
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | markdown-it | ≥ 15.0.0&&< 15.0.2 | 15.0.2npm install markdown-it@15.0.2 |
| 📦npm | markdown-it | all versions | 14.3.2npm install markdown-it@14.3.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for markdown-it, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update markdown-it to 15.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-111759 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
--- CME Mitigation Guidance (2026-10-20) --- Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure. The highest-value action is to disable typographer mode or the smartquotes inline rule across all markdown-it instances processing untrusted user input: upgrade to markdown-it 14.3.2 and 15.0.2 (or the fixed Libgit/Libgit2/Nextcloud/Forgejo/Ansible/Rhoai/Odh Workbench Codeserver Datascience Cpu Py312…Source: Red Hat security advisory for CVE-2026-111759 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2026-111759 in your dependencies?
Find it across npm, including transitive dependencies.