jsx-slack v4.5.1 and earlier versions are vulnerable to a regular expression denial-of-service (ReDoS) attack.

Impact

If attacker can put a lot of JSX elements into <blockquote> tag, an internal regular expression for escaping characters may consume an excessive amount of computing resources.

/** @jsxImportSource jsx-slack */
import { Section } from 'jsx-slack'

console.log(
  <Section>
    <blockquote>
      {[...Array(40)].map((_, i) => (
        <p>{i + 1}</p>
      ))}
    </blockquote>
  </Section>
)

Patches

See also: GHSA-hp68-xhvj-x6j6

jsx-slack v4.5.2 has updated regular expressions to prevent catastrophic backtracking.

jsx-slack v4.5.1 also had patched a workaround. It has no problems to contents with ASCII characters, but still vulnerable to contents with multibyte characters. (36e4a10)

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-43838
• 36e4a10

Credits

Thanks to @hieki for finding out this vulnerability.